Editing using a GPS

Editing in ArcPad with a GPS is very similar to editing with the mouse pointer, pen, or stylus; the main difference is that the GPS is the source of coordinates instead of the mouse pointer. Using the incoming GPS coordinates, you can capture point, polyline, and polygon features. You can also move existing points and vertices to the current GPS position.

There are, however, some differences when using the GPS coordinates to capture and edit with ArcPad:

• Your ArcPad map needs to have a projection defined before you can activate the GPS.

The projection can be defined using two methods:

1. Associate a projection file (.prj) with each layer in your ArcPad map.
2. Use the Select Projection button in the Table of Contents to select a projection file on your computer that matches the projection of the data in your ArcPad map.

• The GPS needs to be activated before any of the GPS buttons on the Edit toolbar are enabled. Furthermore, the GPS Point button is only enabled when a point layer is active for editing. The Add GPS Vertex and Add GPS Vertices Continuously buttons are only enabled when either the polyline or polygon feature type has been selected.

• Optionally, you can specify various quality control parameters to filter out less accurate GPS coordinates. For example, you can specify maximum PDOP or EPE values or limit ArcPad to only use 3D or DGPS GPS coordinates.

• You can also specify alert messages and sounds, which ArcPad displays and plays, respectively, when the specified quality control parameters have been exceeded.

• You can optionally use the average x, y, and z coordinates of multiple GPS positions to capture point features or vertices of polyline or polygon features.

You can also specify the position interval, or frequency, and distance interval of GPS position coordinates for ArcPad to use when capturing polyline or polygon vertices in streaming mode.

The GPS Quality, Alerts, and Capture options are all specified in the GPS Preferences dialog box. These options are also discussed in the GPS Quality, Capture, and Alerts options section.

In most cases, the GPS coordinates received by ArcPad are in latitude and longitude degrees, typically using the WGS84 datum. This may be different to the projection and datum of the data in your map. In this case, ArcPad automatically does on-the-fly projection and datum transformation of the incoming GPS coordinates to the projection and datum of your map data.