Gramrekha Mobile documentation¶
Table of Contents
Introduction¶
About the Gramrekha GIS App¶
Gramrekha Mobile - is a mobile GIS for Android OS.
Gramrekha Mobile allows to:
- display a map from a set of layers;
- perform map navigation (zoom in, zoom out, pan);
- add vector data from GeoJSON format;
- add cached raster data in zip archive;
- add online tile sources (XYZ and TMS);
- add raster and vector layers from Gramrekha Web;
- create and modify vector geodata (geometries and attributes);
- browse the attributes of selected geometry through identify dialog;
- modify the attributes of vector layer with customizable input forms;
- share the resultant vector data locally or in the cloud with variety of Apps;
- record the tracks and manage their display parameters, remove selected or all tracks;
- display coordinates, velocity, altitude of device on the map, as well as a source of geographical coordinates and amount of satellites used for georeferencing (if GPS is used);
- collect and transmit to Gramrekha Web created and/or edited :term:’geodata’ in background mode (when internet connection is on).
Gramrekha Mobile is open source (license GPL v3).
Some icons used in Gramrekha Mobile are from:
- Icons8.com distributed on CC BY-ND 3.0;
- romannurik.github.io - CC BY 3.0.
Documentation is describing Gramrekha Mobile version 2.5.
Hardware and Software requirements¶
To launch Gramrekha Mobile you need a device (smartphone, tablet, etc.) with Android 4.4 or higher.
To be able to use all Gramrekha Mobile features the device should have the following hardware:
Note
If any of these items are missing from the device, the related functions will not be available.
Gramrekha Mobile does not impose specific system requirements. However, the amount of system memory and storage space can limit the size of uploaded geodata.
Installation¶
Gramrekha Mobile can be installed in one of these ways:
- using an APK file gramrekha.apk;
To install from the APK file first allow application installation from unknown sources (“settings/security/unknown sources”). After installation you can deactivate this option.
To launch Gramrekha Mobile use a shortcut created automatically during setup (see Fig. 1).
Application shortcuts.
User interface (UI)¶
There are 3 major elements of Gramrekha Mobile UI:
- Main Screen
- Layers Tree Panel
- Settings Dialog
UI is designed in accordance with Google Material design guidelines.
Main screen¶
Main screen is shown on Fig. 2.
Main screen.
The number of buttons in top toolbar depends on your device screen size. If the buttons don’t fit into the toolbar they are moved to the contextual menu (item 5 in Fig. 2).
Top toolbar contains the following buttons:
- Show my location
- Load or refresh geodata
- Start new track
- Settings
- About
Status info panel (item 9 in Fig. 2) can be shown at the bottom of the Main screen (if it is activated in the Settings). Status info panel shows:
- Device coordinates (latitude and longitude);
- Positioning signal source (mobile networks/Wi-Fi or satellite) and number of captured satellites (if positioning is carried out with help of GPS/GLONASS);
- Device altitude (meters);
- Device speed (kmph)
Depending on the size of the screen Status info panel can occupy one or two rows.
Layers tree¶
Layers tree panel is designed to show the content of a map and to control the visibility and hierarchy of map layers. Additional operations with layers are available from a separate layer contextual menu. Layers tree panel is shown on Fig. 3.
Layers tree panel.
To change the hierarchy of map layers long-press the layer which is to be moved up or down. Layers tree panel will switch to Edit mode. Keep pressing and move the selected layer to its new position.
For turning layer visibility on/off tap on Layer visibility button (item 3 in Fig. 3).
“Add geodata” button (item 4 in Fig. 3), facilitates creating vector layers and importing vector as well as raster layers, from Android local storage, cloud or a few selected web services, as shown below:
Add geodata options
By using “Open local” menu item you can upload geodata from SD card or cloud storage, in one of the following formats:
More information about geodata upload can be found in “Adding layers” section.
Layer contextual menu depends on layer’s type, whether it is Vector or raster. When you tap the Contextual menu button (item 5 in Fig. 3), contextual menue items pop up as shown by item 6 in Fig. 3
- Zoom to extent
- Attributes
- Share
- Edit
- Delete
- Settings
Settings dialogue¶
Depending on the screen size Settings dialogue can fit into one or two panels. Settings dialogue is shown on Fig. 5 (one panel mode).
Settings.
There are following Settings on the main panel:
- General
- Map
- Location
- My tracks
- NextGIS Settings
“General” settings allow to change basic settings of the map (see Fig. 6).
General settings.
Here you can select one of the themes from Light & Dark and select for compass settings.
“Map” settings allow to change basic settings of the map (see Fig. 7).
Map settings.
Map settings include:
- Show/hide Status info panel
- The way current location displays (show current location, show marker, how marker & accuracy radius)
- Show mini compass
- Do not turn off the screen when map displays - works only on the map screen
- Show/hide zoom control buttons
- Show scale ruler
- Show measuring button
- Coordinates format (for coordinates in Status bar and other dialogs and screens)
- Map background (light, dark, neutral)
- Map path (here you can specify a path where map and layers data will be stored)
Note
For devices with several SD cards and Android 4.4 and higher, map path not on the main SD card can only be specified in the application home directory and its subdirectories (for example: Android/data/com.nextgis.mobile). This is also true for some devices without root access. Read-only folders won’t show up in path selection dialog.
“Location” settings offers a few location specific settings (see Fig. 8).
Location settings.
Location settings include:
- Coordinate source (mobile networks/Wi-Fi + GPS, Other networks or only GPS)
- Minimum update time
- Minimum update distance
- Count of GPS fixes
“Tracks” settings are similar to the location settings, but they are applied only for track recording.
Note
If you set value of the minimum update distance at more than 5 m, the operating system will start to smooth the track (remove outliers).
Useful facilities¶
From the Main screen itself the App offers a couple of facilities useful in the field.
Show my location¶
To know your current location, just tap on the “Show my location: button (see item 3 in Fig. 2 above). This will show your current location on the map screen with a marker. If your “status info panel” (see item 9 in Fig. 2 above) is visible via appropriate Map settings (see Fig. 7), you will be able to view the relevant information there itself.
Note
Your “Location” settings must be made ON from your Android mobile settings.
Measure distance¶
It is possible to measure the distance between two points from the map screen in a easy manner. Just tap on the measure button on the map screen (see item 6 in Fig. 2 above). It will give a message like “Tap on map to check points”. Tap on your starting point. A red point with handle appears on the screen. Then tap on your second point. The first point becomes blue & second red dot will appear. A blue line is drawn between the points and the distance appears on the top toolbar. See Fig. 9 below for illustration.
Measure distance.
You can even tap the third point and the distance between first & third point will be captured & shown. This way you can measure distance of a smooth curve, too.
If your third point forms a triangle, then a thin line between the first & third point is seen & the resultant triangle that would form. In this case the system shows the area of that triangle in the top toolbar.
This also applies to any number of points. A polygon may be formed in this way & the resultsnt area.
When you are done, tap the blue tick button to exit the measure mode.
Note
To avail this facility, “Show measuring button” check box must be ticked ON in the map settings. (see Fig. 7).
Adding layers¶
Gramrekha Mobile has the ability to create new empty vector layers or by importing vector as well as raster data from cloud storage or mobile device storage. The supported data types are GeoJSON, cached tiles in a special format and custom forms with vector in a special format.
Creating new vector layer¶
Here are the steps to create an empty vector layer:
- First tap on “Layers tree menu” (item 1 in Fig. 2). Then tap on “Add geodata” (item 4 in Fig. 3). It will pop up a panel as shown below in see Fig. 10. Tap on “Create layer”.
Add geodata Contextual menu.
- In the opened dialog enter the parameters of new vector layer (see Fig. 11)
Parameters of the new vector layer.
The standard form for the creation of new vector layer contains the following parameters:
- Layer name - enter the name of layer which will be displayed in the layers tree.
- Geometry type - select layer geometry type (point, linestring, polygon).
- Fields - list of fields which can be added, edited or deleted. These are attribute values of the layer.
You can add many attributes to a layer. For each attribute creation just tap on “+” button next to Fields. This will open new dialog every time for creation of each field (see Fig. 12) below.
Dialog for creation of a new field.
Dialog for creation of a new field contains the following parameters:
- Field name – enter the name of the field.
Note
The field name can only be entered in Latin characters (letters and numbers!) without spaces. It should also differ from SQL reserved keywords.
- Field type - select field type from one of the (string, integer, real, date&time, date, time)
Creating vector layer from GeoJSON data¶
We can create a vector layer by importing an existing GeoJSON file. To open data in GeoJSON format:
- First tap on “Layers tree menu” (item 1 in Fig. 2). Then tap on “Add geodata” (item 4 in Fig. 3). It will pop up a panel as shown in Fig. 10 above. Tap on “Open local”.
- Select the GeoJSON dataset from your mobile device storage (see Fig. 13). E.g. tap on the file “Roads.geojson” to import the “Roads” vector data file.
Android local storage.
- When the file is selected a layer settings dialog opens. Here you can specify your own layer name or keep the name as it is. (see Fig. 14). E.g. “Roads”.
Layer settings dialogue.
- Pressing “Create” button starts data processing for creation of a new layer.
Note
In case of GeoJSON data importing the new layer will always be a vector layer!
You can check if the new layer was created successfully in the layers tree panel. The newly created layer will show up in the layers tree (see Fig. 15). The “Roads” layer is shown in orange rectangle.
Layers tree panel.
GeoJSON: format requirements
- Coordinate system of input geometries can be WGS 84 (EPSG:4326) or Web Mercator (EPSG:3857) only. If input file has different coordinate system you will see a warning message about unsupported coordinate system.
- All geometries in the file must be of the same type. If input file contains varying types of geometry in the output you will have a file with geometries type that coincides with the type of first record, i.e. geometry of first entry will determine the type of layer geometry.
- Text strings must be encoded in UTF-8 format.
Note
You can read more about the GeoJSON format in its specification. GeoJSON is based on the format JSON (see RFC 4627).
You can only use standard attributes form for editing GeoJSON layer.
It contains the following fields:
- Text field for entering characters or digits.
- Dialog for entering date time.
- “Add pictures” button.
A sample standard attributes form is shown below in Fig. 16.
Standard attributes form.
You can further perform standard edit operations like Add, Modify or Delete operations for this layer. For more information about GeoJSON layer editing see Editing a geometry.
Creating new raster layer from Tile cache (NGRC)¶
Tile cache is a zip-archive with folders and tiles stored in accordance with a tiling scheme (for example, folder_z/folder_x/y.png) and compressed in a file having an extension “.ngrc”. Folders of level Z can be located in the root or in a folder in the root folder (name of the folder doesn’t matter, but there have to be only one folder). Deeper nesting of level Z folders is not allowed.
Follow these steps to open tile cached raster file in ngrc format:
- First tap on “Layers tree menu” (item 1 in Fig. 2). Then tap on “Add geodata” (item 4 in Fig. 3). It will pop up a panel as shown in Fig. 10 above. Select “Open local” (see Fig. 10)
- Select ngrc file from your mobile device storage (see Fig. 17). E.g. tap on the file “Tandali_Wadgaon.ngrc” to import the “Tandali Wadgaon” raster satellite image.
Android local storage.
It will start importing tiles to create new raster layer. You can check if the new layer was created successfully in the layers tree panel. The newly created layer will show up in the layers tree as shown in (see Fig. 18). The “Tandali_Wadgaon” layer is shown in orange rectangle.
Layers tree panel.
Adding Geoservice layer¶
If you don’t have any raster layer in tiled cache format file, it is still possible to add raster data hosted on external servers. Here, e.g. you can import tiles from existing services like Google, Bing, Mapbox, ESRI etc. as a new raster layer.
For this, first tap on “Layers tree menue” (item 1 in Fig. 2). Then tap on “Add geodata” (item 4 in Fig. 3) and select “Open local” (see Fig. 10). Then tap on “Add geoservice” and you will be provided a screen as shown in Fig. 19 below.
Add Geoservice.
Select your service provider and tap “Add” to create layer for that service. It will be shown in the Layer tree.
If you have your own hosting service or have an valid account from private service provider, you can create that layer by tapping “New” in above Fig. 19. It will open up a configuration panel for that layer as shown in Fig. 20 below.
New Geoservice.
Here you can specify the Layer name & Layer URL, The Tile layer type, from XYZ or TMS and the user credentials like Login & Password. This will create a new layer and import tiles from that service into layer.
Note
You need to be Online while adding or creating Geoservice. It will consume your data pack & apply standard Internet charges from the Internet service provider.
Note
Once you created Geoservice layer, you can work in the field Offline, without any Internet or mobile connectivity. But you need to make sure about browsing your area under intervention completely, for all required zoom levels.
Creating new vector layer from Custom forms (NGFP)¶
NGFP files can be generated using NextGIS FormBuilder. NGFP is a GeoJSON file with additional information (JSON) which is packaged in zip archive and has .ngfp extension.
Perform the following steps to add NGFP file to NextGIS Mobile:
- First tap on “Layers tree menu” (item 1 in Fig. 2). Then tap on “Add geodata” (item 4 in Fig. 3). It will pop up a panel as shown in Fig. 10 above. Select “Open local” (see Fig. 10)
- Select NGFP file from your mobile device storage (see Fig. 21). E.g. tap on the file “Structures.geojson” to import the “Structures” vector data file.
Android local storage.
- When the file is selected a layer settings dialog opens. Here you can specify a layer name (see Fig. 22):
Layer settings dialogue.
- Pressing “Create” button starts data processing for creation of a new layer.
You can check if the new layer was created successfully in the layers tree panel. The newly created layer will show up in the layers tree (see Fig. 15). The “Structures” layer is shown in orange rectangle.
Layers tree panel.
NGFP layers use custom (not standard) attributes form optimized for attributes viewing and editing. Custom form contains special controls for editing, such as dropdown lists, radio buttons or linked lists.
Custom attributes form.
You can further perform standard edit operations like Add, Modify or Delete operations for this layer. For more information about NGFP layer editing see Editing a geometry.
Editing layers¶
Gramrekha Mobile allows you to edit vector layers added to the map. While editing, you can:
- add new features;
- delete features;
- edit features.
Switching to Edit mode¶
There are several ways to start edit mode.
- The first way is Main actions button (the big blue button in the right bottom corner of map screen). Pressing Main actions button opens a menu of most common actions (see Fig. 25).
Common actions menu.
You need to tap the pencil button (item 6 in Fig. 25) to go to edit mode.
- The second way to start editing is to long-press the geometry. This will open an Editing Toolbar at the bottom. There you need to tap the “Edit” button to switch on to edit mode (item 3 in ).
- In the third way, tap on “Layers tree menu” (item 1 in Fig. 2). Then tap on the context menu button next to the layer name (item 5 in Fig. 3). This will pop up the context menu itms as shown in item 6 in Fig. 3. There you need to select “Edit”.
The Editing Toolbar¶
After switching to edit mode from any of the above, an Editing Toolbar is opened at the bottom of the map screen. (see Fig. 26)
Editing Toolbar.
Note
This editing toolbar is common for all type of layers, viz, point, line or polygon.
Adding features¶
If you select the first method To add feature to a vector layer by pressing Main actions button, press a pencil icon (see item 6 in Fig. 25). Tap on a layer name, you’d like to edit in an opened dialog (see Fig. 27).
Select layer dialog.
After you select a layer, map screen switches into Edit mode. It displays an editing toolbar at the bottom of the map screen, as shown in Fig. 26. You can create any type of geometry (points, lines or polygons).
Adding a point¶
To add a point to an existing layer first select a point vector layer from any of the 3 methods mentioned above. Then tap on the + icon in Bottom toolbar (item 2 in Fig. 26).
New point will appear in the center of the screen highlighted in red, together with arrow icon. You can move this point any where on the map screen by simply holding the circular handle. The red cross hair marker is left behind at the center of the map screen.(see Fig. 28).
Creating a point.
After new point is added geometrically, you need to set its attributes by tapping on the “floppy” button (item 5 in Fig. 28). Pressing floppy icon will save a new point and open Attributes editing form (see Fig. 29).
Standard attributes editing form.
Once all the attributes are filled, tap on the Tick icon on the right top corner (item 2 in Fig. 29) to save the attributes. If you tap on the back button on the left top corner (item 1 in Fig. 29), the system will warn you of any unsaved changes. The Camera icon at the bottom (item 3 in Fig. 29) facilitates you to open any photograph from the local storage or take a new photograph of the geographic object just digitized.
Adding a line¶
To add a line to an existing layer first select a line vector layer from any of the 3 methods mentioned above. Then tap on the + icon in Bottom toolbar (item 2 in Fig. 26).
New line will appear in the center of the screen, with one of its vertices highlighted in red and with arrow icon (see Fig. 30).
Creating a line.
You can move the vertices any where on the map screen by holding their handle. If you tap on the middle vertex, it will create two extra vertices automatically. Again in their turn you can move & create as many vertices till your purpose is served. In this way you can even get a smooth curve as per the geographic shape.
After new line is added geometrically, you need to set its attributes by tapping on the “floppy” button (item 5 in Fig. 30). Pressing floppy icon will save a new line and open Attributes editing form as shown in Fig. 29 above.
Once all the attributes are filled, tap on the Tick icon on the right top corner (item 2 in Fig. 29) to save the attributes. If you tap on the back button on the left top corner (item 1 in Fig. 29), the system will warn you of any unsaved changes. The Camera icon at the bottom (item 3 in Fig. 29) facilitates you to open any photograph from the local storage or take a new photograph of the geographic object just digitized.
Adding a polygon¶
To add a line to an existing layer first select a line vector layer from any of the 3 methods mentioned above. Then tap on the + icon in Bottom toolbar (item 2 in Fig. 26).
New polygon will appear in the center of the screen, with one of its vertices highlighted in red and with arrow icon (see Fig. 31).
Creating a polygon.
Note
The left 2 buttons are for multi polygon editing, an advanced topic not covered here.
After new polygon is added geometrically, you need to set its attributes by tapping on the “floppy” button (item 5 in Fig. 31). Pressing floppy icon will save a new polygon and open Attributes editing form as shown in Fig. 29 above.
Once all the attributes are filled, tap on the Tick icon on the right top corner (item 2 in Fig. 29) to save the attributes. If you tap on the back button on the left top corner (item 1 in Fig. 29), the system will warn you of any unsaved changes. The Camera icon at the bottom (item 3 in Fig. 29) facilitates you to open any photograph from the local storage or take a new photograph of the geographic object just digitized.
Adding current location¶
To add current location to a vector layer press Main actions button, and then press a pushpin icon (item 7 in Fig. 25). In an opened dialog select a layer you’d like to add current location to (only point geometry layers will be displayed) (see Fig. 32). If there is only one points layer available, it will be selected automatically.
Select layer dialog.
Current location will be added to selected layer as a new point consisting of 1 point.
Further actions are same as in “Adding a point”.
Note
You can add current location to Point geometry layers only!
Adding line or polygon by tracking¶
To add line or polygon by tracking to a vector layer press Main actions button, and then press a walking man icon (item 5 in Fig. 25). In an opened dialog select a layer you’d like to add current location to (only line and polygon geometry layers will be displayed) (see Fig. 32).
Find more information about this & further topics at Record tracks to vector layer.
Note
You can add tracks to either Line or Polygon geometry layers.
Editing a geometry¶
To edit an existing layer first select that vector layer from any of the 3 methods mentioned above and enter the editing mode. The feature will turn its colour to Blue. Then tap on the pencil icon in Bottom toolbar (item 3 in Fig. 26). The feature will turn its colour to Red in edit mode.
Editing a point¶
To start editing a point it should be first selected by pressing on it. It will change its colour to blue. Then tap on the pencil icon in Bottom toolbar (item 3 in Fig. 26). The selected point feature will be highlighted in red and have an arrow pointing at it.
To change location of a selected point simply pull it or arrow pointing at it to a desired place. Also a point can be moved using buttons from Bottom toolbar - to the center of the screen shown as Red Crosshair marker (item 6 in Fig. 33) or to the current device location (see item 7 in Fig. 33).
You can cancel editing at any point of time, without saving changes, by close editing button. (see item 1 in Fig. 33). The system will warn you about this.
In the end you can have your geofeatures digitized as shown below. See Fig. 33.
Editing point
Editing a line¶
To start editing a line it should be first selected by pressing on it. It will change its colour to blue. Then tap on the pencil icon in Bottom toolbar (item 3 in Fig. 26). The line will change its colour to red and will show all its vertices. Current vertex is highlighted in red and has an arrow pointing at it. The center of line segment between vertices is also indicated. Pressing the center of line segment leads to two new vertex being added to the line.
New vertex can be moved or otherwise edited right after it has been added. Also a vertex can be moved using buttons from Bottom toolbar - to the center of the screen shown as Red Crosshair marker (item 7 in Fig. 34) or to the current device location (see item 8 in Fig. 34).
You can delete the unrequired vertex by highlighting it and tapping delete vertex (see item 6 in Fig. 34)
In this way you can even get a smooth curve as per the geographic shape.
In the end you can have your geofeatures digitized as shown below. See Fig. 34.
Editing line
Note
If only one vertex remains in a line this line is deleted automatically.
Editing a polygon¶
To start editing a polygon it should be first selected by pressing on it. It will change its colour to blue. Then tap on the pencil icon in Bottom toolbar (item 3 in Fig. 26). The polygon will change its colour to red and will show all its vertices. Current vertex is highlighted in red and has an arrow pointing at it. The center of line segment between vertices is also indicated. Pressing the center of line segment leads to two new vertex being added to the line.
New vertex can be moved or otherwise edited right after it has been added. Also a vertex can be moved using buttons from Bottom toolbar - to the center of the screen shown as Red Crosshair marker (item 7 in Fig. 35) or to the current device location (see item 8 in Fig. 35).
You can delete the unrequired vertex by highlighting it and tapping delete vertex (see item 6 in Fig. 35)
In the end you can have your geofeatures digitized as shown below. See Fig. 35.
Editing polygon
Editing attributes¶
After layer is in edit mode as explained before, an editing toolbar, as shown in Fig. 26, appears in the bottom of the map screen. You need to tap on “Attribute info” (see item 5 in Fig. 26). This will open Attribute info panel as shown in Fig. 36 below.
Attribute info
Note
When you tap on to view attributes (see item 4 in Fig. 36),
- For Point layer, system shows that point’s current location in Latitude/Longitude by default.
- For Line layer, system shows the length of that line features in meters by default.
- For Polygon layer, system shows the perimeter of that polygon feature in meters & the area in square meters by default.
Editing attributes using standard form¶
You need to tap on “Set attributes” button (see item 6 in Fig. 36). This opens a standard attribute editing form as shown in Fig. 29. Once all the attributes are filled, tap on the Tick icon on the right top corner (item 2 in Fig. 29) to save the attributes. If you tap on the back button on the left top corner (item 1 in Fig. 29), the system will warn you of any unsaved changes. The Camera icon at the bottom (item 3 in Fig. 29) facilitates you to open any photograph from the local storage or take a new photograph of the geographic object under intervention.
The Attributes toolbar¶
The Attributes toolbar is common for all the geometric features, viz. point, line or polygon, as shown below in Fig. 37
Attributes Toolbar.
Note
This Attribute Toolbar is common for all type of layers, viz, point, line or polygon
The attribute table¶
Tap on “Layers tree menu” (item 1 in Fig. 2). Then tap on the context menu button next to the layer name (item 5 in Fig. 3). This will pop up the context menu itms as shown in item 6 in Fig. 3. There you need to select “Attributes”. Attribute table for that layer opens as shown in Fig. 38 below.
Attributes Table.
Here you can tap on any record (row) in the table. Attribute table toolbar appears at the bottom of the screen. This facilitates a few actions for that record with corresponding ID as shown below in Fig. 39.
Attributes table toolbar.
You can open the standard attribute form for editing as shown in Fig. 16 by selecting “Open attribute editing form” (see item 8 in Fig. 39)
Warning
If you tap on “Delete” button (see item 7 in Fig. 39), the system deletes the feature momentarily although providing undo menu, live for 5 seconds. If undo action is not selected, the feature gets deleted permanently.
Editing attributes of a custom form¶
If the layer includes customized attributes form (layer created with a ngfp file), instead of standard one (see Fig. 29), the following form as shown below in Fig. 40 will be used in Edit attributes dialog.
Custom attributes form.
Customized attributes form may contain the following entry fields:
- Text;
- Space;
- Text field;
- List; Tandem list;
- Checkbox;
- Radio button;
- Date Picker;
- Photo.
“Text” field is used to provide additional information about created geometry. “Text field” can be used to add text or integers, depending on the field type (see item 4 in Fig. 40).
“List” and “Tandem list” fields are used to store and select values included in custom lists, for example, “List” - region/republic/territory, “Tandem list” - district/area in region/republic/territory (see item 5 in Fig. 40).
“Radio button” field allows to select one element from a list of mutually exclusive options (see item 7 in Fig. 40).
“Date picker” field allows to select date, time or both of them (see item 6 in Fig. 40).
After filling in all required attributes press Tick button (item 2 in Fig. 40) to save edits.
Pressing buttons 1 or 5 will return you to Map screen. The system will warn you about any unsaved changes.
Layer settings¶
Map is a set of raster and vector layers. Order and visibility of layers are configured in layers tree. There is a sliding panel of layers tree in a user’s interface where composition of the map is displayed as a set of layers. It allows to change the order of layers and enables or disables their visibility.
You can perform further operations with the layers by tapping layer context menu (item 5 in Fig. 3). It will pop up a list of menus as shown in item 6 in Fig. 3.
Menu for the vector type has a following composition.
- Zoom to extent
- Attributes
- Share
- Edit
- Delete
- Settings
Note
Layers menu depends on its type. Raster layer has different context menus than that of a Vector layer.
Vector layer settings¶
Tap on “Settings” from the layer menu to configure it. A panel opens as shown in Fig. 41 below.
Vector layer settings.
Above Fig. 41 shows a Simple Render. In this Render type all the features have same colour which can be set through “Fill color” (see item 7 in Fig. 41). It also facilitates the stroke colour setting through “Stroke color” (see item 7 in Fig. 41). The sizes of both of these can be changed by typing appropriate size in “Size” & “Width” respectivelly (see items 5 & 8 in Fig. 41).
You can even select shape of the object by selecting “Type” (see item 6 in Fig. 41). You can select from 1. Circle 2. Diamond 3. Cross 4. Triangle 5. Box
You can also show or hide one more important style feature, Lable text. You can make it appear by selecting “Text” and select the field to appear as shown in item 9 in Fig. 41.
For advanced styling of vector layer select “Rule” in the Render. It will open another list of menus as shown in Fig. 42 below.
Rule based vector style.
select the field from available fields list to render as rule (see item 2 in Fig. 42). Then tap on “NEW” (see item 3 in Fig. 42). It will pop up a panel showing all the unique values from that selected field. Select the value one by one & tap on its name to open the styling panel as shown below in Fig. 43
Rule based field item.
Here you can select the Stroke colour & size of the feature as well as the label text to show based on the attribute field. Select “OK” when finished. Thus you can configure all the values within that field and render them on map screen.
To select which field to render as Label, tap on the “FIELDS” menu and select one of the field as shown in Fig. 44
Select field for Label.
The “GENERAL” menu shows information about layer as its path, name & allowed zoom levels to show. It is possible to show the layer within certain zoom levels only. For rest all other zoom levels it will be invisible on the map screen. See Fig. 45 below.
Style vector General menu.
The “Rebuild cache” item in “CACHE” menu is used to optimize the processes of a layer creating with the ability to save and cancel changes.
Raster layer settings¶
Context menu of raster layer has the following composition (see Fig. 46):
- Zoom to extent
- Delete
- Settings
Raster layer menu.
Tap on “Settings” to open raster layer settings. It will open up the raster layer settings panel as shown in Fig. 47 below.
Raster layers settings.
You can set the values for
- Opacity. The value of layer opacity determines how intensive it hides or displays the contents of the underlying layer. Layer with 1% opacity is substantially transparent. Completely opaque layer has an opacity of 100%.
- Contrast. Contrast of the layer can be changed to spice up the image.
- Brightness. Brightness of layer can be changed to make image darker or lighter.
- Greyscale (the color image mode value of grayscale brightness values expressed in percent. 0% is a white color (the absence of black pigment on a white background), 100% is a black color).
The “GENERAL” menu shows information about layer as its path, name & allowed zoom levels to show. It is possible to show the layer within certain zoom levels only. For rest all other zoom levels it will be invisible on the map screen. See Fig. 48 below.
Raster General menu.
The “Rebuild cache” item in “CACHE” menu is used to optimize the processes of a layer creating with the ability to save and cancel changes.
Tracks¶
Gramrekha Mobile allows to record and display tracks. Recorded track points are saved to the internal database. Track points recorded within one session are combined and displayed on the map as a line.
Note
Make sure that the Location mode is active in your Android mobile phone settings. Also check the configurations of “Location” settings from Gramrekha App settings contextual menu, as shown in Fig. 8.
Recording a track¶
Tracks can be recorded in two ways.
Record & export tracks in GPX¶
To start recording a track press “Start new track” button in the Contextual menu on the Main screen (item 5 in Fig. 2).
Track recording is performed in background mode. To indicate that the process is running a status icon of the walking man is displayed in Android Notification bar. For more information just open it and it will show the status as shown in Fig. 49 below.
Recording track status.
When the track recording is done, we see on the map screen the path traced so far, as shown below in Fig. 50.
Recorded track is displayed on the map immediately. We have not stopped tracking yet. The status icon (walking man) is still seen in the notification bar. The green flag shows the starting point of the track where as the location marker shows the current location.
To stop tracking open notification bar & tap on “Stop” (see item 4 in Fig. 49). The status icon now vanishes, The location marker gets repalced by the red flag indicating end of the track and the track is visible in different colour as shown below in Fig. 51.
The GPX track is now ready for export. To know more about exporting the tracks, see _ngmobile_export_GPX.
Track points are grouped by days and sessions within a day. If track recording continues the next day, track will be split up into two parts.
Record tracks to vector layer¶
We can also add a feature to an existing line or polygon vector layer by tracking.
For this, tap on “Action button” (see item 8 in Fig. 2) & then tap “Geometry by tracking” (see item 5 in Fig. 25). It will open list of Line & Polygon vector layers in a separate panel as shown below in Fig. 52.
Line & Polygon Layers tree.
Select the layer to which you need to add the feature by tracking. This will open that layer in editing mode as shown below in Fig. 53.
Vector layer editing by tracking
When you tap on “Location” setting (see item 6 in above Fig. 53) it will open the “Location” settings of NextGIS App (see Fig. 8).
When tracking is finished tap on the “floppy” button (see item 4 in Fig. 53). It will open the standard attribute editing form, similar to Fig. 29, as shown below in Fig. 54.
Vector layer attribute editing
The newly added track is now part of the geometry feature of that line or polygon vector layer.
Managing recorded tracks¶
To start managing tracks first find “My Tracks” group layer in Layers tree. It is shown in the orange box. Then select the “Settings” item in a contextual menu as shown in Fig. 55. Tap on “List”.
Layers tree.
This will open list of recorded tracks as shown in Fig. 56 below.
List of recorded tracks.
When you select the track by ticking on the Chekbox in front of it, buttons in Top toolbar will become active as shown in :numref:`ngmobile_layer_gpx_selected_pic`below.
Toolbar for selected track.
To hide that layer, tap on “Open eye” (shown in item 6 in Fig. 57).
When you tap to open contextual menu (see item 5 in Fig. 57), the associated menu items pop up as shown below in Fig. 58.
Tracks contextual menu.
- Here you can Show or Hide the selected track in the map screen. The starting point is shown in Green markere & the end point is shown in Red marker.
- You can delete the track (permanently).
- You can select all the tracks and perform above actions for all at a once.
Exporting data¶
Exporting data in GeoJSON¶
To export data from Gramrekha Mobile vector layer, tap on “Layers tree menu” (item 1 in Fig. 2). Then tap on the context menu button next to the layer name (item 5 in Fig. 3). This will pop up the context menu itms as shown in item 6 in Fig. 3. There you need to select “Share”. Android standard Share dialog window with a list of available Share options will open as shown in Fig. 59.
Share dialogue window.
After you select a share option, data in the selected layer will be recorded in GeoJSON format (coordinate system Web Mercator, EPSG:3857) and exported using the selected application. A name of the GeoJSON file corresponds to the name of the layer.
- You can send the file as attachment via your email App or Gmail.
- You can upload it to Google Drive, which may or may not be shared with your colleague.
- You can share it to another Android mobile via Bluetooth or SHAREit.
- You can even copy it on to your laptop via Bluetooth, if possible.
Note
In a lot of Android versions to save a file on the device memory card you need a file manager app (for example, ES Explorer or similar).
Exporting attachments¶
Each feature in vector layer can have 1 or more photos attached to it. Photos are stored separately as image files and added to archive file with layer data during the export. For each feature a separate attachments folder is generated in the archive, the name of the folder correposnds to feature ID.
Example:
(4:10000002.jpg,10000000.jpg,10000001.jpg,10000003.jpg)
Explanation:
4 photos are attached to a feature. These 4 photos are stored in the folder which name correposnds to ID of this feature.
Exporting tracks in GPX¶
To start exporting tracks first find “My Tracks” group layer in Layers tree. It is shown in the orange box. Then select the “Settings” item in a contextual menu as shown in Fig. 55 and tap on “List”.
Layers tree.
This will open list of recorded tracks as shown in Fig. 56
To export the track, tick on the Chekbox in front of its name. The buttons in Top toolbar will become active as shown in Fig. 57.
To share the track, tap on Share button (see item 4 in Fig. 57). It will open the same “Share dialogue window” as shown in Fig. 59 above. Further operations are in the similar manner.
Glossary¶
- Android
- Android
- Android is a mobile operating system developed by Google, based on the Linux kernel and designed primarily for touchscreen mobile devices such as smartphones and tablets. Android has the largest installed base of all operating systems (OS) of any kind. Android has a growing selection of third-party applications, which can be acquired by users by downloading and installing the application’s APK (Android application package) file, or by downloading them using an Google Play Store that allows users to install, update, and remove applications from their devices.
- Cloud
- Cloud Computing
- Cloud computing is a type of Internet-based computing that provides shared computer processing resources and data to computers and other devices on demand. It is a model for enabling ubiquitous, on-demand access to a shared pool of configurable computing resources (e.g., computer networks, servers, storage, applications and services), which can be rapidly provisioned and released with minimal management effort. Cloud computing and storage solutions provide users and enterprises with various capabilities to store and process their data in third-party data centers, that may be located far from the user–ranging in distance from across a city to across the world.
- Coordinate System
- Geographic Coordinate System
- A geographic coordinate system is a coordinate system that enables every location on Earth to be specified by a set of numbers, letters or symbols. The coordinates are often chosen such that one of the numbers represents a vertical position, and two or three of the numbers represent a horizontal position. A common choice of coordinates is latitude, longitude and elevation.
- Geodata
- Geodata
- Geodata is collection of geographic features & asociated information about them, also known as spacial information.
- GeoJSON
- GeoJSON
- GeoJSON is an open standard format designed for representing simple geographical features, along with their non-spatial attributes, based on JavaScript Object Notation. The features include points, linestrings & polygons and multi-part collection of these types.
- GIS
- Geographic Information System
- A Geographic Information System is a system designed to capture, store, manipulate, analyze, manage, and present spatial or geographical data. In general, the term describes any information system that integrates, stores, edits, analyzes, shares, and displays geographic information. GIS applications are tools that allow users to create interactive queries (user-created searches), analyze spatial information, edit data in maps, and present the results of all these operations. GIS is a broad term that can refer to a number of different technologies, processes, and methods. It is attached to many operations and has many applications related to engineering, planning, management, transport/logistics, insurance, telecommunications, and business. For that reason, GIS and location intelligence applications can be the foundation for many location-enabled services that rely on analysis and visualization.
- GLONASS
- “Global Navigation Satellite System”, is a space-based satellite navigation system operating in the radionavigation-satellite service and used by the Russian Aerospace Defence Forces. It provides an alternative to GPS and is the second alternative navigational system in operation with global coverage and of comparable precision. Manufacturers of GPS devices say that adding GLONASS made more satellites available to them, meaning positions can be fixed more quickly and accurately (location to within 2 meters).
- GPS
- Global Positioning System
- The Global Positioning System (GPS) provides geolocation and time information to a GPS receiver in all weather conditions, anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites. The GPS system operates independently of any telephonic or internet reception, though these technologies can enhance the usefulness of the GPS positioning information. The GPS system provides critical positioning capabilities to military, civil, and commercial users around the world. The United States government created the system, maintains it, and makes it freely accessible to anyone with a GPS receiver.
- Raster
- Raster
- Raster image is a dot matrix data structure representing a generally rectangular grid of pixels or cells. The information is stored in a cell.
- Tile
- Tile
- These are square images sorted by the grid, displaying the map, often with size of 255 X 255 and in PNG format.
- TMS
- Tile Map Service
- Tile Map Service or TMS, is a specification for tiled web maps, developed by the Open Source Geospatial Foundation. The definition generally requires a URI structure which attempts to fulfill REST principles. The TMS protocol fills a gap between the very simple standard used by OpenStreetMap (XYZ) and the complexity of the Web Map Service standard, providing simple urls to tiles while also supporting alternate spatial referencing system.
- URL
- Uniform Resource Locator
- A Uniform Resource Locator (URL), commonly informally termed a web address, is a reference to a web resource that specifies its location on a computer network, like Internet, and a mechanism for retrieving it.
- Vector
- Vector
- In a GIS, geographical features are often expressed as vectors, by considering those features as geometrical shapes. Different geographical features are expressed by different types of geometry as, Points, Lines & Polygons. The information about these features is stored in an attribute table.
- XYZ
- Raster Tile Map
- Slippy map (in OpenStreetMap terminology) or Tiled Web Map is a map displayed by seamlessly joining dozens of individually requested image files over the internet. It is currently the most popular way to display and navigate maps, replacing other methods such as WMS which typically display a single large image, with arrow buttons to navigate to nearby areas. X, Y & Z denotes the numbering scheme to serve the images. The images are commonly of the size 256 X 256 in PNG format.
Index and Tables¶
- Index
- Search Page
- glossary