Exercise Mobile Gis and Gps

ASSIGNMENT MOBILE GIS AND GPS

Remote sensing & GIS-oriented cases of AMC2 Environmental Sciences

Wageningen University, Centre for Geo-Information Sytze de Bruin Version: April 2006

Introduction Mobile GIS is a growing technology. More and more options are becoming available for field spatial data collection and on-location presentation of GIS and spatial information via mobile devices In this exercise you will practice with some specific mobile GIS technology, which is offered to you for use during the course.

Goals After this exercise you are able to:  Interpret basic terminology related to the used mobile GIS technology;  Display image data and vector data on a PDA (Personal Digital Assistant) with ESRI® ArcPadTM;  Activate a Bluetooth GPS connection on a PDA;  Show the current GPS position in an ArcPad map;  Capture and save point data at the current GPS position;  Capture and save arc vertices (lines) using GPS positions;  Store attribute data in an editable ArcPad layer;  Save an ArcPad map;

Materials Each group is provided with:  PDA, with cradle, USB connector, battery charger, protecting sleeve;  Bluetooth GPS receiver;  Image (rectified aerial photograph, 2000) and vector data (top10vector, 1995)  ESRI ArcPad Quick Reference.

1 Assignment

Upload the data for this assignment to the PDA using the instructions listed in the document “Upload_data_ArcPad.pdf” which is in the Document Library Resources of https://portal.wur.nl/sites/GRS cases YES60506 .  Switch on Bluetooth on both devices: on the GPS unit this is achieved by a hardware on/off switch; on the PDA, use the IPAQ Wireless communication manager (see below)

IPAQ wireless communication manager, use Press the indicated button by the white arrow to either the menu option or the shortcut. switch on Bluetooth on the PDA. The encircled button activates the Bluetooth manager  Couple the devices using the Bluetooth Manager. After pressing the Manager button (see above), tap New, and select the last option “Explore a Bluetooth device”. All active Bluetooth-enabled devices within in a radius of approximately 10 meters will be displayed on the screen. Therefore, you should be at some distance from other groups. Tap on the GPS device to set its behaviour; the subsequent screens should be similar to the ones below.

 Tap BT GPS  Select SPP slave  Next Press and hold to connect

 Start ArcPad, use the Add Layer button to add the layers alterra_zoom.jpg and Clip_Top10.shp which are in the directory “pond_gps” to an empty map and zoom in to the area covered by the aerial photograph. Note that for some reason, the OK button is obscured in ArcPad as it is currently installed on the PDA.  Create a new Point layer (Shapefile); add a text field named “DESCRIPT”, with length 20; Save it as “Testpoint” in the folder “pond_gps”; make this layer editable. Tips: use New Layer from the OPEN MAP DROPDOWN LIST to create a layer; open the Layers dialog box to make a layer editable.  Activate the GPS using the relevant option from the GPS POSITION WINDOW DROPDOWN LIST.  Walk to a few topographical features that you wish to add to the layer “testpoint” and enter the relevant data using the Capture Point Using GPS from the EDIT/DRAWING TOOLBAR. After entering a description press the ‘Enter Key’ ( ) on the keyboard, otherwise your point is NOT saved!!!!  Save the map as “Firstmap” in the folder “pond_gps”.  Deactivate the layer “Testpoint..shp” and create a new Polyline layer; add a text field named “DESCRIPT”, with length 20; Save it as “Testline” in the folder “pond_gps”; make this layer editable.  Add a new line feature corresponding to the path around the pond located north of the Alterra East building to “Testline.shp”. Tips: use the Add GPS Vertices Continuously option from the EDIT/DRAWING TOOLBAR. The first vertex of the polyline must be entered by hand by activating the Polyline feature type and tapping the screen at a relevant starting point. Save the polyline tapping the Polyline button. Add a relevant description. After entering the description press the ‘Enter Key’ ( ) on the keyboard, otherwise your line is NOT saved!!!!  Save the map as “Secondmap” in the folder “pond_gps”.  Copy the data to the Tablet PC.  Show your results to a member of the staff.

3 Troubleshooting No current position fix available - without tracking three satellites the receiver cannot provide a reliable 2-dimensional position fix. You may have to wait for the satellites to move into positions from which they can be seen. GPS units don’t work indoor, underwater or underground. Prevent blocking the GPS antenna with your hands or body.

No data is being received from your GPS receiver. If --owing to the power saving settings-- the PDA switched off, you have to re-establish the BT GPS connection. First, de-activate the GPS in ArcPad; next, use the BT Manager to reconnect the BT GPS (see Figure on lower right of page 2). Else, check whether the ArcPad settings are correct by selecting Options from the TOOLS DROPDOWN LIST. Settings should be as follows:

The GPS position is incorrect. The receiver must track at least three satellites which are well distributed around the visible sky so that the satellites measurements provide good ‘Geometric Dilution of Precision’ (GDOP). Quite often, misregistration problems result from using incorrect projection information. The data used in the course are all in Rijksdriehoekstelsel: the Dutch grid. Data should be accompanied by a correct .prj – file, i.e copy Rijksdriehoekstelsel.prj to the folder where your data are and rename it to .prj. The Datum method option from the Layers dialog box should be set to “Position Vector”, as follows:

4 The System folder under the ArcPad install folder (e.g. \Program Files\ArcPad\System) on the device should have a file named apDatums.dbf. This file contains the necessary projection parameters.