Environmental Measurements: Digital Locations

GPS Locations

GPS locations are recorded in two different ways: waypoints and tracks. You actively cause the recording of a waypoint (single location, date and time). Tracks are a series of points (locations, date and time) that are recorded as long as the GPS is operating and this function is enabled.

You need to be able to handle both styles of recording, including downloading the data and interpreting the results.

Equipment manuals show how to make the recordings in both styles.

Download GPS data using GPStracker software. Important note: Don't save the file on a Garmin GPS before downloading. If the file is saved on the Garmin GPS, the time information is lost!

Examples

Waypoint data

Trailhead (so you can return to this location, including knowing how long it will take)
Specimen collection site
Interview location

Track Data

Photo locations (software will link photos and locations if the GPS and camera clocks are set to the same time)
Drawing of the route taken
Link locations to activities (if notes were taken about the times at which activities occurred)

Digital Maps

Drawing a Map

PowerPoint (or its OpenOffice equivalent) lets you trace on top of a drawing.

Site Maps

Site maps provide an interpretation of an area. For example, how is an area around a community used?

Some points to consider:

What is the appropriate resolution of the map?
What is the necessary accuracy?
What is the trade-off between the effort in producing the map and the required accuracy?
What tools are available to simplify the process?
What quality is required in the final product?

Some general workflow suggestions:

Define the use of the Site Map, including the general appearance of the final product (e.g., publication quality?)
Delimit the overall area to be included in the map.
Obtain photo imagery of the region (e.g., Google Maps) and determine its adequacy.
Discuss the appropriate classification of the area with people who are familiar with the region.
Discuss the important site features, including access (e.g., roads, gates), landmarks, buildings, and historical features.
Plan field measurements in the context of the available information and photo imagery.
Carry out field measurements (e.g., GPS waypoints and tracks, tape measure, compass lines).
Create preliminary Site Map.
Re-interview people familiar with the region to obtain their feedback on the accuracy of the Site Map (classification and site features).
Finalize the Site Map and distribute it to appropriate people (including those who held in its creation).

Examples:

(Kahana Valley)

(Kahe Power Plant region)

Software Requirements

GPStrackmaker: Used to transfer data (both waypoints and tracks) from the GPS into a stored PC file.
OpenOffice (PowerPoint): Draw maps (especially as they overlay satellite photos)
Google Earth: Satellite image resource, geographic coordinate finder, and as a map/satellite image integrator
GeoSetter: Link a track log to photos (via timestamping)

Please Note: There is a lot of development in this field. A good way to keep up, or look for alternative software, is to check the Free Geography Tools blog.

An Introduction to GPS for Field Ecologists

The Three Functions of a GPS Receiver

Marking: Record Locations
Tracking: Record Paths
Find Locations

How a GPS Reciever Works

Satellites (the Constellation)
Precise clocks
Model of the Earth
Time-triangulation

Constraints to GPS

Geometry of the satellites
Clear view of the sky (including the bouncing signal problems)
Atmosphere

Function 1: Recording Locations

"Mark" locations and record the date and time

Function 2: Tracking

Recording a string of locations (with date and time)

Function 3: Finding Locations

Downloading data from a Garmin GPS

Requirements

Garmin receiver with a USB cable
PC software: GPS Trackmaker
Optional: www.gpsvvisualizer.com

Workflow

Plug in the Garmin GPS to a computer with the USB connection
Power on the Garmin GPS
Run GPS Trackmaker
Click on the GPS menu and choose Garmin Interface ...
Use the popup menu and confirm that the Garmin GPS is identified (if not, you may need to Exit and restart the Garmin Interface ...).
Click on Waypoints and then Tracklogs (wait for the download; progress is shown in the information panel).
Exit when done.
(Power off the Garmin GPS)
Click on the File menu and choose the Save File as ...

If the GPS has just the desired data, do the following:

Use the popup menu; browse to the appropriate location, enter an appropriate file name and choose the GPX file type.

If you want to edit the GPS track log or waypoints:

Use the popup menu; browse to the appropriate location, enter an appropriate file name and choose the TXT file type.
Open the TXT file in an editor such as Textpad (not a word processor).
Look at the data and trim out any lines that are not wanted.
Save the edited file.
Go to the web page for GPS Visualizer.
Use the file conversion panel by browsing to your TXT file; Choose the GPX file type as your output. Click the Go! button and wait for the conversion.
A new web page will appear. Right click on the name of the converted file, choose Save File as ...
Provide an appropriate file name and location.

The GPX files can be dragged onto Google Earth.

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