In order to yield consistently high-precision GIS maps, it’s a must that you use best practices for your GPS/GNSS data collection.
The problem is, mapping and GIS professionals are sometimes misled (or never properly trained on) what the best practices for GIS data collection are. That’s a pretty big deal, especially when you consider that the product specifications mean nothing if you’re not using the device properly.
When a device isn’t giving you the correct accuracy, the majority of the time it’s likely due to incorrect settings, mismatched GPS reference frames or inaccurate data collection practices. A small percentage of the time it may be due to a marginal mapping environment and multipath, but with Trimble mapping and GIS solutions, even in what were once challenging GPS environments, poor precision is rarely caused by the GPS/GNSS receiver being incapable of yielding the desired accuracy.
This means that it’s up to you as the user to take the proper steps in order to ensure the best possible outcome. As they say, “with great power comes great responsibility.”
If you’re seeking high-precision results: Use a range pole!
If your mapping application requires high-accuracy positions, best practices for GIS data collection dictate that you use a range pole. If you are attempting to achieve repeatable decimeter (or greater) precision, this is a must. Otherwise, you are investing in the cost of higher-precision technology and time in the field while yielding very low accuracy.
Be mindful of your terrain
If you’re dealing with tree canopies, buildings or canyons, you’re prone to poor satellite reception or geometry, which can severely impede your ability to collect precise GNSS data – if any data at all.
If there is too much obstruction preventing you from getting a strong satellite signal, you can always utilize a laser rangefinder to automatically offset the position of your GNSS antenna while standing in a clear, open view of the sky – to the features that you’re trying to collect that may reside beneath the aforementioned obstructions.
Measure precise elevations
In order to get an accurate elevation measurement, you need to ensure that you are using a range pole that allows you to take into account the vertical offset from the feature that you are measuring to the center of the GPS/GNSS antenna. The type of GNSS receiver technology also makes a significant difference in the quality of your elevation data. Single frequency, code-based receivers can yield centimeter-level vertical results, but only if you occupy a point for several minutes (to hours), and have a reference receiver collecting data nearby that can be used to post-process your roving data; whereas multi-frequency, carrier-based receivers such as the Trimble R2, Geo7X or the Spectra SP20 are capable of measuring centimeter-level elevations in real time.
Collect it accurately the first time around…
It may be the case that you don’t need high-accuracy right now. But if you should ever need to achieve more precise elevation measurements later, you don’t want to have to re-do the work just in case your requirements have changed.
Your greatest expense is having staff in the field (salaries, insurance, vehicles, etc.). If you purchased a high-accuracy receiver, it’s vital to take the time to learn how to use it properly in order to get the most of its capabilities.
No matter what you’re told, failing to use essential accessories such as range poles with higher-precision GNSS for mapping and GIS applications can eliminate any additional precision that your GPS/GNSS receiver was designed to yield. In order to learn more about GPS data collection best practices, CSDS is here to help.
Learn more about GIS data collection
Are you looking for a way to drastically improve your accuracy and consistency? Is your current receiver not achieving the results you need?
Call CSDS at 800-243-1414 to ask a question, request a quote, or receive a product demonstration. One of our Mapping & GIS specialists will be in touch to share their expert opinion on solutions that will work best for your company’s needs.
For more information on the concepts and practices recommended above, please leave a comment or send an email to firstname.lastname@example.org.
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