How To Set Up A GPS Receiver To Collect GIS-Compatible Data During Ecological Surveys

20 Oct

In the last ten years, GPS receivers have gone from being a relatively specialist piece of equipment to something that almost anyone can afford. The accuracy of these units has also improved dramatically over time and it is now possible for almost anyone to collect accurate spatial data when conducting ecological surveys. At the same time, the use of Geographic Information Systems (GIS) in ecological research has also blossomed, and being able to use GIS is now rapidly becoming a must-have skill for ecologists. However, while these two technologies have developed in consort, uniting them is not always as straight-forward as it might at first seem. In particular, if you wish to use data collected using a GPS receiver in a GIS project, you need to first ensure that your GPS is set up appropriately. Here are the most important settings you need to check before you start using your GPS receiver to collect your survey data.

1. Check what projection/coordinate system your GPS receiver is set to record locational data in: Like GIS projects, GPS receivers can be set to record data in a variety of projection/coordinate systems. This means that you need to make sure yours is set to an appropriate one before you start. In most cases, this will be the Geographic Coordinate System (GCS), meaning that your positions are recorded in latitude and longitude. However, you could also choose to set your GPS receiver to record positions in a local or regional projection/coordinate system, such as the British National grid.

2. Check what datum is being used for your selected projection/coordinate system: As well as setting the projection/coordinate system, you need to also set the datum. For most GPS receivers, the default will be WGS 1984 and this will be fine, but in some circumstances, you might want to use a different one. In addition, you should never assume that your GPS receiver is using the WGS 1984 datum. If you do not use the right datum, you may find that the positions of your data are out by up to 1km when you come to plot them in your GIS project.

3. Check the format that your positions will be recorded in: GPS receivers can display and record positional information in a variety of formats, and it is important you know which one yours is using. Typically, this will be degrees and decimal minutes, but you could also select the more traditional degrees minutes and seconds, the GIS-ready decimal degrees or even a local coordinate system such as the British National Grid eastings and northings. The one you select is up to you, but it is important that you know which one it is.

4. Check what reference point is being used for your headings, bearings and courses: Headings, bearings and courses are all displayed in degrees. However, you can select from two possible reference points. These are either True North or Magnetic North. There can be a difference of up to five degrees or more between these two (depending on where you are in the world), meaning it is important to know which reference point your GPS receiver is using. This is also important if you are using your GPS for navigation.

5. Check the time settings: It is important to know whether your GPS receiver is displaying time in a 12 or 24 hour format, and also what time zone is being used for your times. While it is usually fine to let your GPS receiver select the appropriate time zone automatically, if you are conducting a survey across the boundary between two time zones, you might want to select a standard one so that all temporal data are recorded using a standardised time.

6. Check the units that are being used for distance and speed: It is important that you know what units are being used to measure distances and speeds. For most ecological surveys, you will want to select the metric system, but in some cases, you may want to use other systems.

7. Check how any automatically collected data are going to be recorded: Many GPS receivers allow you to automatically record the track that you take. However, before you start using this function, you need to ensure that it is collecting this information at appropriate intervals. The default for most GPS receivers is to record this information automatically, but for most ecological applications, you will want to record your track positions at regular intervals. These can either be intervals of time or distance.

Once you have checked these settings for your GPS receiver, you can use it safe in the knowledge that any data you collect will be GIS compatible. If you do not check these settings, you may find that when you come to add your data to your GIS project that you cannot do so because you do not know what setting your GPS receiver was using to collect your data. You should check these settings each time you go into the field, especially if you are sharing it with anyone else who might be using different settings. Similarly, if you are working with a group of people to collect ecological survey data, it is important that you check that everyone’s GPS receivers are using the same settings before you start. This ensures that all the data collected will be compatible with each other, and with the GIS project that it is going to go into.

For a video demonstration on how to check these settings for a GPS receiver, visit the GIS In Ecology You Tube Channel, or simply click here.

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