How to digitize an area?

As we mentioned before, if you wish to have the area computed for a region of land or water on a raster image, you must first draw the boundary line around that region and save it as an Area Feature. An Area Feature is a vector shape and can be saved in the shapefile format.

To digitize an Area Feature in iCMTGIS or iGPSGIS, first select an existing Area Topic or create a new Area Topic.

To create a new Area Topic, tap the Main Menu, select Topic then select New Topic. Enter a Topic  Name, such as “Fields”. Make sure the Type field shows: Area. Tap the green check mark to confirm the screen and return to the Map View.

To activate an existing Area Topic in order to add a new Area Feature to this group, tap the Topic View icon on the upper-right corner of the main screen then select the desired Area Topic. Tap the Topic View icon again to hide the list of Topics.

When an Area Topic is active, and you tap the pull-down arrow for the Tools icon next to the Main Menu icon, you will see that the Add Area manually tool is active (not grayed out). Tap this selection, and the Add Area manually tool icon will be displayed.

Now, tap the vertices of the desired polygon, or trace the curvilinear outline of an irregular area.

While you are digitizing, if you need to zoom in or out, first tap on the little hand with a pointed index finger. This will halt the digitization mode and reactivate the regular touch-screen mode. Tap on this toggle again when you are ready to continue with the digitization.

If there are existing Features on the map and you want a node to snap to one of the existing Features, then tap the SnapTo Node tool showing an arrow pointing to a node. When the SnapTo Node toggle is on, the node you add will be dropped on top of the nearest Point or node.

When you have digitized the last node for the Area Feature, tap the Add Area manually tool again. The software will automatically close the gap between the first and the last digitized nodes.


4 Responses to How to digitize an area?

  1. Dave Schuler says:

    Our company has a need for a GIS/GPS tool to map and measure farm fields and groves. We need a tool with which our field staff can, with minimual training, map and measure area in acres by walking around the field or damage area. We also need mapped polygons preferably in Shape file format and we’d then like to transfer these polygons to our web based GIS platform.

    Does your application provide this functionality? For both iPhone and iPad? could you provide documentation or demo of these functions?

    • cmtinc says:

      iCMTGIS II for iPAD and iGPSGIS II for iPhone provide the functionality to easily map and measure areas such as farm fields and groves. These apps will let the users load a Google Map as the background so they will be able to see the mapped polygons in relation to the surrounding geographic features. The mapped points, lines and polygons can be exported in Shapefile format, which can be transferred to your desktop computer, emailed, or sent out via ftp.

      We have been providing user-friendly GPS/GIS data collection software for years to foresters and farmers with minimal computer knowledge. The GPS/GIS data collection functions in iCMTGIS II and iGPSGIS II are based on our Microsoft Windows Mobile FieldCE GIS data collection software, which is widely used by foresters and farmers (such as the American Sugar Beet Seed Association, the OSU Department of Agriculture, farms in California, etc.).

      The iCMTGIS II and iGPSGIS II app include a Help document that describes all the functions in the app. Many tips on using the software are also provided at this site. Please check out the July and August blog posts related to data collection. It is rather simple to have your field staff walk around an area to map it. If you want them to also record a description and/or other information for each polygon then you would set up a Feature List and train them to select the appropriate attribute/value to record with the polygon.

      iCMTGIS II is listed at $94.99 and iGPSGIS II is listed at $44.99. You could try the less expensive one first.

      Please keep in mind that the accuracy of positions and acreage will depend on the GPS receivers used. If your farm acreages or damage areas are small, you may need to employ a GPS system with higher precision, such as our ALTO-G12 GPS data collector, which is a more expensive system.

  2. Dave Schuler says:

    quick reply…thank you. will iCMTGIS & iGPSGIS accept GPS signal from add on GPS devices for the iPAD or iPhone?

    • cmtinc says:

      iCMTGIS II and iGPSGIS II use the Apple iOS standard API. We have not tested these apps with all external GPS devices for the iPAD and iPhone, but we expect them to work with a compatible GPS device such as the Dual XGPS150. (XGPS150 provides a free app for viewing the visible satellites and the signal strength.) If you find it to be otherwise, please let us know.

      Update: We have confirmed that our iCMTGIS II, iGPSGIS II and Deed Calls – Area – Perimeter apps do work with the Dual XGPS150 Bluetooth GPS receiver.

      By the way, here is the link to a demo showing how to pair the Dual XGPS150 with an iPAD.

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