Preparing for a GIS mapping job

You will be able to perform your data collection job more efficiently if you plan ahead and get the answers to the following questions first.

1) What are the accuracy requirements on the GPS data to be recorded?

Barring human errors, your GPS data will be as good as your GPS data collection system. Please keep in mind that, at this time, mapping grade GPS devices are like measuring sticks with 1 – 5 m graduations.

2) What type of Features will you be mapping?

Some people are only intersted in mapping Points. Others may also need to map routes or areas. When you map a path or an enclosed area, please keep in mind that the attribute information will be recorded for the entire Line Feature or Area Feature, rather than for each node on these lines or areas.

3) How long do you plan on occupying each Point? How often would you like to log GPS positions while moving along a path?

You know, instead of entering this parameter for each Feature that you record, you can predefine it in a Feature List using iGPSGIS or iCMTGIS. Then whenever you select a Feature Topic from the Feature List to log data for it, the relevant data collection parameters will be automatically applied.

4) What attribute information would you like to record for each Feature Topic?

If you collect data for multiple Features with different characteristics, you want to organize them and group similar Features into Feature Topics. You can define a set of Attributes for each Feature Topic and also pre-define the Values for each Attribute. When using such a Feature List for data collection, you can easily select the applicable descriptions for each recorded Feature instead of entering the descriptions by hand.

5) Will you need to use existing data or a background map as reference for this data collection job?

iGPSGIS and iCMTGIS can display the built-in Map as the background.

PC-GIS PRO will let you import data in various popular formats then save it in a .pmp file for use on the iGPSGIS for iPhone, iCMTGIS for iPAD, or Field CE GIS for Windows Mobile PDA. It will also enable you to prepare raster images for use on the mobile device.

If you have a Windows-based tablet PC or notebook PC running PC-MAPPER, then you can load the background image in various formats (e.g. TIFF, GeoJpeg, MRSID, ECW).

PC-GIS PRO and PC-MAPPER will let you geo-reference your own aerial photos for use as background maps.

The CMT PC software will also covert the neat CMT Basemaps into a format that can be used in your iOS or Windows Mobile device. The PC application can even let you select roads and landmarks from the CMT Basemap to convert them into Features.

6) Do you need to visit known locations to record new observations?

You could import these locations as Shapefiles. Or, you could digitize these locations in iGPSGIS or iCMTGIS.  Then edit the coordinates to match those for the exact location.

PC-GIS PRO and PC-MAPPER will also let you import coordinates in other formats (e.g. ASCII, DXF, Excel, KML, GPX).

7) Does your data collector have sufficient power in it to complete the job?

Make sure the battery in your data recording device is fully charged. Take an extra set of battery along if the device will use replaceable battery.

8) Are the GPS satellites up there favorably configured?

Once or twice a day, the relative positions of the GPS satellites may be such that the location solution cannot be precisely determined. This type of error is called DOP (Dilution of Precision). If you have the CMT PC-GPS or PC-MAPPER software, you can use the Mission Planning function to find out ahead when those peaks occur on the day you plan to do your field work. Otherwise, when you see that the horizontal/vertical accuracy displayed in iCMTGIS or iGPSGIS is not good, you can try waiting half an hour then resuming your job.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s