Implementing Portable GIS : the Guide
Terminology
GIS Geographic Information Systems: (not to be confused with GPS) are a means for creating, storing, and analyzing spatial data.
GPS Global Positioning System: (not to be confused with GIS) is a satellite-based navigation system that can be extremely useful for collecting spatial data.
dGPS Differential GPS: An extremely accurate, but usually more expensive, base station based GPS.
Mobile GIS: essentially allows one to perform GIS tasks in the field with GPS, handheld computers, and/or any other portable electronic device available. This could include data collection, data storage and/or data analysis.
Data Collection
GPS is the obvious means of in the field data collection. Other means of electronic data collection – Total Station, theodilite – are unwieldy, relatively slow, often more expensive, and over-accurate for the type of work we do. The only viable competition to the GPS is to not implement anything if a cost/benefit analysis indicates as much.
GPS Implementation
What is required:
- An accurate handheld GPS or dGPS…
…with mobile GIS software (preferably)
…with USB access
- Necessary training
Data Collection WITH
There are several mobile GIS applications on the market; that being said, ESRI’s ArcPAD is the most used and most directly compatible with the GIS software we have (ArcView 9.2).
What is ArcPad?
It is, essentially, a scaled down, mobile version of ArcMap. It allows the user to store, view and record geographic information on a handheld computer at any location. For instance, an air photo can be underlayed in background while tree points are recorded in real time.
Possible Methodology for Data Collection WITH
1) Record point, line, or polygon features on the fly
2) Assign them to a layer of your choice or create a new layer
3) Add annotation on screen via keypad or by freehand drawing with stylus
4) Plug the unit into an ArcMap enabled PC and directly import the recorded layers to a GIS
5) Symbolize the data appropriately for use in map outputs, geodatabases, etc…
Possible Methodology for Data Collection without
1) Record point or area in the field with GPS
2) Record some kind of annotation, be it on paper or on a PDA, that indicates what feature is at each point location
3) Import recorded points into ArcGIS. Create layers for each of the points (e.g. tree species, shrubs), while attaching annotated data from handwritten notes/PDA.
4) Symbolize the data appropriately for use in map outputs, geodatabases, etc…
Draw backs
1) Recording separate notes can be both time consuming and awkward in sordid weather (if notes are on paper).
2) A missed or misplaced point can be very difficult to identify without returning to the field
3) Can not save data as layers or symbolize data
4) Can not underlay existing data/imagery
Bottom line: if mobile GIS can create efficiency that outweighs its price, then it is worthwhile.
Portable GIS for Navigation
A portable GPS that is mobile GIS capable could help navigate to features in the field more quickly. The rough average of ten meters of accuracy that our current GPS possesses is appropriate to locate large features (e.g. a river), but when the goal is to find an individual piece of vegetation it can be a detriment. In addition, ten meters of accuracy can be even lower when in dense forest growth.
Current Technology
- inaccurate handheld GPS
- HP iPAQ hx2000 series with possible GPS integration
- ArcView 9.2
Possible Technology
- Trimble GeoXH handheld GPS (or equivalent GPS)
- ArcPad software
