Defining GPS data collection parameters
July 21, 2011 Leave a comment
For the sample data collection job that we are discussing, our goal is to inventory all the fire hydrants and all the street trees in a section of a city.
Normally, you would use the CMT PC-GIS software to easily set up one or more Feature Lists then port them over for use on your iCMTGIS or iGPSGIS. However, if you need to create a new Feature List or modify an existing one in the field, you may do so by using your iCMTGIS or iGPSGIS. The procedure is as follows.
Tap on the “GPS” icon then select Feature List.
Tap the “Open” button and select the built-in Feature List, named park.fbr. Tap the “Save As” button and save it as a new Feature List under the File Name ht.fbr.
Keep the “Tree” Feature Topic and delete all the others.
Double-tap on “Tree” then add an “s” to it.
Tap the “Add” button and add a new Feature Topic, named “Hydrants”.
Now we have our two Feature Topics of interest: “Trees” and “Hydrants”.
Tap the Tree Feature Topic and make sure the Type field shows “Point”, and the Mode field shows “Static Time”. Change the Time Session to 30. This is the number of seconds you are supposed to stay at each street tree to record its GPS location.
Do the same for the “Hydrants” Feature Topic because these are also Point Features.
The data collection parameters you specify for each Feature Topic will be displayed as the default settings when you select that Feature Topic to collect data for it. You may override the default settings for the Mode field and its associated time parameter.
If you were asked to record the street as a Line Feature, then you would add a new Feature Topic and select “Line” as the Type and “Dynamic Time” as the Mode. The Time Interval field defaults to 1 (GPS fix per second) but you could change it to a higher number if you just want to trace the path roughly.
Similarly, if you were recording the perimeter of a park as an Area Feature, then you would add a new Feature and select “Area” as the Type and “Dynamic Time” as the Mode. You could use the default Time Interval of 1 second, or change it to some other value.
If you were recording a polygon shape and do not care about the nodes between the vertices, then you would select “Area” as the Type and “Static Time” as the Mode. In this case, you would occupy each vertex for the duration of the Time Session to record its location. And nothing would be recorded while you walk or drive from one vertex to the next.