Mobile mapping

version 1. November 2006

Arnel Rala

International Rice Research Institute

[!!!UNDER CONSTRUCTION!!!!]

Contents

I. INTRODUCTION 2 COMPONENTS 2 Data logger 2 GPS receiver 2 Software 3 II. DATA LOGGER 5 CONSERVING POWER 6 III. ARCPAD 10 ARCPAD INTERFACE 10 CONNECTING THE GPS RECEIVER 10 ACTIVATING THE GPS RECEIVER 12 DATA CAPTURE USING GPS 14 Configure GPS related settings 14 Creating New Point Features 16 Creating New Polyline or Polygon Features 19 APPENDIX 1: ARCPAD TOOLBARS AND TOOLS DESCRIPTION 20 MAIN TOOLBAR 20 BROWSE TOOLBAR 21 EDIT TOOLBAR 22

I. Introduction Mobile mapping provides user with the ability to collect field data, with unique geospatial time tags and attributes, for integrating into or updating a GIS database. Mobile mapping provides the freedom to collect data anytime, anywhere, in any manner. It comprises the integration of four technologies: GIS, lightweight computing device, GPS receiver, and wireless communication. Components Data logger A lightweight computing device that runs the GIS software, stores data and communicate with a GPS receiver. An example is HP 3970 or HP 5550. GPS receiver Trimble Pathfinder Pocket A small, lightweight, portable, rugged and weatherproof GPS receiver. Compared to other receivers, the receiver’s low profile means that it does not restrict your mobility.

Key features: • continuous tracking of up to 8 satellites • 2–5 meter accuracy after differential correction • 1 second position and velocity update rate • autonomous accuracy to 10 meters • supports output of NMEA 0183 messages

DeLorme Blue Logger GPS Another GPS device, but operates on Blue tooth technology – meaning wires are no longer needed to communicate data to the data logger. It also has the new SiRF GPS chips that can track 12 satellites. Among its other features are as follows; • NMEA 2.0-compliant 12-channel receiver • WAAS-enabled SiRF • Memory for 50,000 logged points • Maximum Velocity: 1000 knots • Maximum Altitude: 60,000 feet

Software ArcPad ArcPad provides database access, mapping, GIS, and global positioning system (GPS) integration to users out in the field via handheld and mobile devices. Data collection with ArcPad is fast, easy, and significantly improved with immediate data validation and availability.

With ArcPad, you can; • Use existing data—ArcPad supports industry-standard vector and raster image display. • Add data from the Internet—Data can be provided from the Internet via wireless technology. • Move around your map—ArcPad includes a number of map navigation tools including zoom and pan, spatial bookmarks, and center on the current GPS position. • Query your data—Identify features, display hyperlinks, and locate features. • Measure distance, area, and bearings on your ArcPad map. • Navigate with your GPS—Connect a GPS and let ArcPad guide you. • Edit your data—Create and edit spatial data using input from the mouse pointer, pen, or GPS.

GPSCorrect for Arcpad Is an enhancement to the standard ArcPad software that improves position quality and reliability by enabling postprocessed differential correction of GPS data in Shapefiles. It also provides an easy management of GPS and real-time differential GPS (DGPS) settings to ensure that data collected in the field meets the required quality.

Other features of GPSCorrect are; • Graphical displays provide immediate feedback on GPS status and position quality, for more efficient fieldwork. • Interactive mission planning shows the best times of the day to collect GPS data, to ensure time spent in the field is productive

Figure 1. Mobile GIS kit setup

Figure 2. Mobile GIS at work

II. Data logger The iPAQ runs on Windows CE or Pocket PC 2002 operating system which is based on the Microsoft Windows operating system but is designed specifically for handheld PCs. Preinstalled software are the Microsoft Pocket Office suite (including Pocket Word, Excel, Internet Explorer, and Outlook), Terminal Services, MSN Instant Messenger for Pocket PC, MS Reader and Voice Recorder as well as handwriting recognition. There is other 3rd party software as well. Utilization of these bundled software will not be discussed here but is available from the companion CD.

The iPAQ has a 3.8” transflective thin film transistor (TFT) color liquid crystal display (LCD) with 65,536 colors and a resolution of 240 x 320. However, in outdoor operation, it is difficult to read the display even at maximum brightness level. Battery is a rechargeable 1400mA lithium ion with a battery life of 4-8 hours during outdoor operations.

The iPAQ has 48MB Flash ROM with 22 megabytes available in FileStore for your use and 64 MB built-in RAM. The built-in secure digital (SD) slot and the compact flash (CF) expansion pack provide a facility to increase storage capacity. GIS or GPS data should be stored in the SD/CF media.

Conserving power Because your iPAQ Pocket PC uses some power to maintain files in RAM and the clock, you need to recharge the battery regularly. Keep the iPAQ Pocket PC connected to the universal cradle or the AC adapter while you are at your desk and DC adapter plug when traveling.

The following is a collection of suggestions for conserving power so you could have more time out in the field.

1. Exit programs not in use Figure 1 shows the main interface of Windows CE. The icons on the bottom right corner are icons of currently opened programs that are in the minimized state. Tapping the icon will bring the program back to a maximized state. Turning off the unit by pressing the power button will not close running programs regardless of their state (i.e., minimized or maximized). Programs that are running but are not being used must be explicitly closed by exiting the application.

2. Deactivate bluetooth radio A blue light blinking on the top right corner of the iPAQ unit means the Bluetooth radio was accidentally activated and is consuming power. To turn the radio off, tap the rightmost blue icon (the one with a circle and two arrows in it) located on the bottom of your screen and select Turn radio OFF. Figures 2 and 3 show the radio in its on and off states, respectively.

          Figure 1			    Figure 2			   Figure 3

3. Sound Settings Information about hardware and device properties, as well as configurations for the Windows CE can be viewed and changed in Settings. You can get to it by tapping the Start menu from the taskbar (refer to Figure 4). Settings has three tabs – Personal, System, and Connections (Figure 5). Under Personal, the Sounds & Notifications setting controls the sounds associated with events (Figure 6). Enabling the sounds only for the important events and setting the volume to a modest level will also help conserve power.

Figures 4 Figure 5 Figure 6

4. Power settings Power settings and information can be accessed from Power menu under System setting (Figure 7). Power menu has two submenus – Main and Standby. The Main Power setting displays the remaining battery power as well as the control for auto-shutdown (Figure 8). The critical level for batter power is at 10% but recharging of the battery is recommended to be done once the power level drops to 50%.

Figure 7 Figure 8 Figure 9

When digitizing long polylines using the GPS, timer for the auto-shutdown MUST be disabled to prevent data loss. This can be done by unchecking the Turn off device if not used for under the battery power. Otherwise, it would be best to enable auto-shutdown to prevent power drain during inactivity.

The Standby Power setting, on the other hand, allows you to adjust the battery standby period (Figure 9).

5. Memory settings Memory resource can be configured in Memory setting under the System menu. Memory has three sub-settings – Main, Storage Card, and Running Programs. Main displays the memory allocation control for Storage and Program (Figure 10) while Storage Card displays the status of the internal storage medium and, if present, the external Compact Flash Card (Figure 11). The last section, Running Programs, shows the list of currently opened applications. Some of the listed applications may not be needed anymore but they are still residing in the memory so you may opt to terminate them by tapping their names on the list and tapping the Stop button.

Figure 10 Figure 11 Figure 12

III. ArcPad ArcPad is software for mobile GIS and field mapping applications using handheld and mobile devices. ArcPad provides field-based personnel with the ability to capture, analyze, and display geographic information. Field data collection with ArcPad is efficient and accurate and can integrate input from GPS receivers, rangefinders, and digital cameras. Providing a visual display of a location (base maps which include administrative boundaries, road networks and aerial photos) helps the user verify and collect information from a location of interest. This section provides an overview in using ArcPad integrated with a GPS receiver. ArcPad interface Figure 1 shows an ArcPad window with four toolbars (1-4), a map window (5), and a status bar (6). The user does not have to see all four toolbars. ArcPad, by default, loads only the Main toolbar (1) and the Browse toolbar (2). The Edit toolbar (3) has to be activated from the Toolbars menu and the GPS Correct toolbar (4) is part of an extension application which means it does not come with ArcPad and has to be installed.

Refer to Appendix 1 for a listing of the tools and menus available from the ArcPad toolbars.

Figure 1. ArcPad interface.

Connecting the GPS receiver The GPS receiver is connected to the data logger physically by wire or virtually by Bluetooth. Trimble Pathfinder Pocket GPS connects to the data logger using a serial sync cable. In contrast, DeLorme Blue logger GPS connects to the data logger wirelessly using Bluetooth technology. The data logger blue tooth radio must be activated for this to take effect.

Once connected, the GPS communication parameters in ArcPad have to be set to match the parameters set on the GPS receiver. The communication parameters are set in ArcPad Options dialog box specifically in the Protocol tab and the GPS tab. The Protocol tab (Figure 2) is used to specify the protocol and datum to be used together with other settings. The GPS tab (Figure 3) is used to specify the communication port, baud, parity, data bits, and stop bits among other settings.

Figure 2 Figure 3

Below are the settings for the two GPS receivers:

Trimble Pathfinder Pocket GPS 1. In the Protocol Tab a. enable ‘Automatically Activate’ b. Select ‘Trimble GPSCorrect’ if GPSCorrect is installed, else select NMEA 0183 as the Protocol to use. c. Select ‘WGS84’ for GPS Datum d. Disable ‘Use Height in Datum Transformation’ 2. In the GPS tab (Do not alter the controls other than those specified below) a. Select ‘COM1’ for Port b. Select ‘9600’ for Baud c. Select ‘None’ for Parity d. Select ‘8’ for Data e. Select ‘1’ for Stop bits

DeLorme Blue Logger GPS 1. In the Protocol Tab a. enable ‘Automatically Activate’ b. Select NMEA 0183 as the Protocol to use. c. Select ‘WGS84’ for GPS Datum d. Disable ‘Use Height in Datum Transformation’ 2. In the GPS tab (Do not alter the controls other than those specified below) a. Select ‘COM8’ for Port (depending on the port assign by the Bluetooth manager) b. Select ‘4800’ for Baud c. Select ‘Odd’ for Parity d. Select ‘8’ for Data e. Select ‘1’ for Stop

Activating the GPS receiver The GPS receiver is activated automatically each time ArcPad is started and the GPS position window is displayed (Figure 4). However, there are times when the GPS does not activate automatically. Manually activate the GPS by tapping on the GPS Position button . This will display a message box informing the user that the GPS device is not activated and inquires if the GPS should be activated (Figure 5). Tap Yes to activate the GPS and display the GPS Position window.

Figure 4 Figure 5

The GPS Position Window The GPS Position Window displays a variety of information about the satellites, position coordinates and navigational information (Figure 6)

Figure 6

Position Coordinates – displays the computed coordinates of a position being observed. The displayed format can be altered by selecting a predefined list of coordinate systems. Tap and hold the stylus on the Position Coordinates to access the coordinate systems menu. Doing so only changes the displayed coordinates and does not affect the projection of the coordinates used for GPS data capture.

GPS mode - displays either No Fix, 2D, 3D and Differential as the type of position being calculated by the receiver.

Elevation – displays the altitude or depth when GPS mode is 3D. Measurement format is changeable by tapping and holding this field.

Skyplot/Signal chart/Compass – pertains to the graphical portion of the window. Skyplot is displayed by default. Tapping in this area will display the other graphical information in a cyclic manner. Skyplot displays the position, pseudorandom noise (PRN) number, and availability of satellites. Availability is color coded where black stands for available and being used to compute position, blue is available but not used and red is unavailable. Signal chart shows the relative signal strength of the satellites (Figure 7). Compass shows the GPS direction with a black arrow and the direction to the selected destination by a red dotted line and a red point (Figure 8).

Figure 7 Figure 8

Navigational information – displays the speed over ground (SOG), Course over ground (COG), Distance to destination (DST) and Bearing (BRG).

Position Measure of Quality – displays a variety of information such as Position Dilution of Precision (PDOP), Horizontal Dilution of Precision (DOP), Vertical Dilution of Precision (VDOP), Time Dilution of Precision (TDOP), Estimated Horizontal Position Error (HPE), Estimated Vertical Position Error (VPE), Estimated Position Error (EPE), number of satellites used to compute position (SATS), Differential data age (DAGE), Differential reference station ID (DSID). Data Capture using GPS Configure GPS related settings ArcPad includes a number of user-specified options that can be used to control which of the incoming GPS coordinates (also known as GPS fixes) are used for creating and editing features. You can use these options to ensure that ArcPad only uses those GPS coordinates that meet your accuracy requirements for data capture. The GPS Quality, Capture, and Alerts options can be specified in the respective tabs in the Option dialog box.

Quality thresholds ArcPad uses quality thresholds to filter GPS fixes and ignores those that do not meet the requirements. The specified options have no influence on how the GPS receiver actually computes the position coordinates, nor do they affect the way ArcPad displays the GPS position. Quality thresholds are set in the Quality tab (Figure 9). The following are the thresholds:

a. Maximum Positional dilution of Precision (PDOP) – quality control is placed on PDOP of incoming GPS positions. The generally acceptable PDOP is 6. It is recommended to have this setting checked. b. Maximum Estimated Position Error (EPE) – this setting is valid only for Garmin receivers. Leave this setting unchecked. c. Differential GPS (DGPS) only – leave this setting unchecked since we do not have the facility for real time DGPS. d. 3D Mode only – quality control is placed on the altitude status of incoming GPS positions. This can be checked or unchecked depending on data needs.

The quality thresholds are enabled or disabled by selecting one of the three warning levels; a. if ‘Compulsory warning’ is selected, the specified quality threshold applies and no GPS data will be recorded if the thresholds were exceeded, b. if ‘Non-compulsory warning’ is selected, the specified quality threshold applies however the user is given the option to record the GPS data or not, c. if ‘No warning’ is selected, none of the specified threshold is applied.

Figure 9

Data capture rules This section defines how GPS data is to be recorded base on the feature type. Data capture rules are set in the Capture tab (Figure 10). The following are the rules:

Enable averaging – it is recommended to have this rule checked to improve the accuracy of the captured GPS position. If enabled, the number of GPS fixes has to be specified for points and vertices.

Streaming Vertices interval – specifies the interval between GPS fixes before GPS data is recorded.

Figure 10

Creating New Point Features The following outlines the steps in capturing GPS positions as point features 1. Create a new point layer or select an existing point layer to store the GPS position(s). a. To create a new point layer, tap New layer from the dropdown list next to the Open Map button (Figure 11). This will open the New shapefile dialog box (Figure 12) where the feature type and database fields are defined. Choose point (or pointZ if you intend to store altitude data) as the feature type (Figure 13) and add field(s) by tapping on the + button. A window will open (Figure 14) where you will be able to define your field(s). Repeat this step until all required fields are defined. Tap OK when done and provide the name, storage folder, and storage location to the Save as dialog box (Figure 15). The new shapefile is automatically added to the map layer list and by default this new layer is editable.

Figure 11 Figure 12

Figure 13 Figure 14

Figure 15

b. To select an existing point layer for editing, tap the Layer button to display the list of map layers (Figure 16). The list is divided into 4 columns with column 1 to toggle visibility, column 2 lists the layers name, column 3 to toggle the display of identify information and column 4 to toggle editing. Enable editing of the target point feature by tapping on the checkbox.

Figure 16

2. Activate GPS - The GPS has to be activated it to start receiving GPS fixes. Under the GPS Position Window in the Main toolbar, select GPS Active (Figure 17). A red box around the icon of the GPS Active means it is in the active state.

Figure 17

3. Tap GPS point button to create a point feature. The Feature property dialog box is displayed (Figure 18). The geography tab shows the X and Y coordinates as well as the Z or M only if the feature is designed to store such information. If averaging is enabled, a progress bar is also shown which counts down the number of GPS fixes to average. The attribute tab displays all the fields in the database and this is where attributes for the point are keyed in.

Figure 18

Creating New Polyline or Polygon Features The process of capturing polyline or polygon features using GPS is the same with the steps outlined in capturing point features. The only difference is the use of the Add GPS vertex or the Add GPS Vertices Continuously button. The former captures single vertices while the latter continuously captures vertices in the current line or polygon feature using the current GPS position. It is important to remember that the feature type is active for data capture (Figure 19 and 20).

Figure 19 Figure 20

Appendix 1: ArcPad toolbars and tools description Main Toolbar

Tools 1. Open Map Open an ArcPad Map (a file with an .apm extension). 2. Save Map Save the current ArcPad map. 3. Add Layer Add one or more layers to the current map. 4. Layers Open the Layers dialog box. 5. GPS Position Window Open or close the GPS Position Window. 6. Tools Open the ArcPad Options dialog box. 7. Help Open the online help.

Open Map dropdown list

	New Map		Close the current map and create a new map.
	New Layer		Create a new shapefile and load it into the current map.
	Open Map		Open an ArcPad Map (a file with an .apm extension).
	Save Map		Save the current ArcPad map.
	Save Map As	          Save the current ArcPad map with a new name and/or in      
                                        a different folder.
	Map Properties	Enter the title of the current map.

Recent Files Display the nine most recently opened maps. Recent Layers Display the nine most recently added layers.

	Exit			Close ArcPad.

Add Layer dropdown list

	Add Layer		Add one or more layers to the current map.
	Add Internet Server	Add an ArcIMS image service as a layer to the current            
                                        map.
	Geography Network	Go to the www.geographynetwork.com website, using 
                                        the default internet browser.

GPS Position Window dropdown list

	GPS Position Window	Open or close the GPS Position Window.
	GPS Active		Activate or deactivate the GPS.
	GPS Tracklog	Start or stop storing GPS points in the tracklog 
                                           shapefile.
	GPS Debug		Open or close the GPS Debug window.

Tools dropdown list

	Options		Open the ArcPad Options dialog box.
	Scale Bar		Display or hide the scale bar.
	Pan Frame		Display or hide the map panning frame.
	Scale Bar		Display or hide the scale bar.

Toolbars Display a sub-menu containing all the toolbars in

                               ArcPad.

Help dropdown list

	Help Topics		Open the online help.
	About ArcPad	Open the About ArcPad dialog box.

About Extension Display a sub-menu listing all loaded ArcPad

                                extensions.

Browse Toolbar

Tools 1. Zoom In Zoom in on map using the pen. 2. Zoom Full Extent Zoom to the full extent of the map. 3. Go Back to Previous Extent Zoom back to the previous extent you

                                          were  using.

4. Identify Activate the Identify tool. 5. Find Open the Find tool. 6. Clear Selected Unselect the selected feature. 7. Refresh Redraw the map.

Zoom In dropdown list

	Zoom In		Zoom in on map using the pen.
	Zoom Out		Zoom out on map using the pen.
	Pan			Pan the map using the pen.

Zoom Full Extent dropdown list

	Fixed Zoom In	Zoom in on the center of the map by 25%.
	Fixed Zoom Out	Zoom out on the center of the map by 25%.
	Zoom To Selected	Zoom to the extent of the selected feature.
	Center on GPS	Center the map on the current GPS position.
	Zoom Full Extent	Zoom to the full extent of the map.
	Zoom To Layer	Zoom to the extent of a particular layer in the map.

Go Back to Previous Extent dropdown list

	Go Back To Previous Extent	Zoom back to the previous extent you 
                                             were using.
	Go To Next Extent	Zoom forward to the next extent in the extent history.
	Set View Coordinates	Set the map extent or center the map at 
                                           specified coordinates.
	Set Map Scale	Set the map scale.
	Create Bookmark	Create a spatial bookmark
	Manage Bookmarks	Edit or delete existing spatial bookmarks.

Zoom To Bookmark Zoom to an existing spatial bookmark.

Identify dropdown list

	Identify		Activate the Identify tool.
	Measure		Measure distances in the map view in point mode.
	Radial Measure	Measure radial distances in the map view using the
                                           pen.
	Freehand Measure	Measure distances in the map view in freehand mode.
	Hyperlink		Activate the Hyperlink tool.
	Go To Selected Feature	Activate the Go To tool.
	Advanced Select	Activate the Advanced Select tool.

Edit Toolbar

Tools 1. Select Activate the Select tool. 2. Vertex Activate vertex display and editing for the selected feature. 3. Point Activate the point feature type for data capture. 4. Capture Point Capture a point feature in the editable point

                                          layer using the current GPS position. 

5. Capture Vertex Capture a single vertex in the current line or polygon

                               feature using the current GPS position. 

6. Capture Vertices Continuously capture vertices in the current line or polygon feature using the current GPS position. 7. Properties Open the Feature Properties dialog box (or custom

                                           edit form) for the selected feature.

Select dropdown list

	Select			Activate the Select tool.
	Select using GPS	Select the feature at the current GPS position.

Point dropdown list

	Point			Activate the point feature type for data capture.
	Line			Capture a straight line feature using the pen.
	Polyline		Activate the polyline feature type for data capture and 

start a new line feature.

	Freehand Line		Capture a freehand line feature using the pen.
	Rectangle		Capture a rectangle polygon feature using the pen.
	Polygon		Activate the polygon feature type for data capture and 

start a new polygon feature.

	Ellipse			Capture an ellipse polygon feature using the pen.
	Circle			Capture a circle polygon feature using the pen.
	Freehand Polygon	Capture a freehand polygon feature using the pen.

Feature Properties dropdown list

	Properties			Open the Feature Properties dialog box (or 

custom edit form) for the selected feature.

	Zoom to Selected Feature	Zoom to the selected feature.
	Center on Selected Feature	Center the map on the selected feature without 

changing the current map scale.

	Go To Selected Feature	Set the selected feature to be the current 

destination for navigation.

	Delete				Delete the selected feature.

Source: ArcPad online help