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An Introduction to Coordinate Systems in Trimble GIS Workflows

Published Date
Author Trimble Geospatial

Coordinate Systems in Trimble GIS Workflows

A Blog Series

Introduction

One of the most fundamental concepts in GIS data collection workflows, and in fact GIS in general, is that of location. High accuracy GNSS receivers and workflows exist mainly for the purpose of improving the accuracy of the location data that we collect. When we collect a location for a feature, that location could be just a point or a collection of points in a line or polygon. Each point, or coordinate, reflects the three dimensions of the measurement. In order for those feature coordinates to be useful, they need to be consistent - they need to use the same coordinate system.

In the vast majority of GIS data collection workflows, feature data will transit through one or more systems, or applications, between field and office. Each of these systems (including that of the GNSS itself) introduces different constraints on the coordinate system. Ideally, the workflow will allow data to be seamlessly integrated into the system-of-record without loss of data fidelity and with minimal loss of accuracy. In order to accomplish this, the coordinate systems used at each step have to be carefully defined and managed; differences between coordinate systems have to be explicitly handled.

A primary contributor to errors when converting GNSS measurement to GIS feature geometries is incorrect handling, or understanding of, coordinate systems. For example, failing to properly handle differences in GNSS and GIS coordinate systems in North America can cause a GIS feature “offset” of up to 1.5 m.

Illustration of a GIS worker experiencing a GIS feature offset

Errors are frequently seen when comparing coordinates of newly collected GIS features with previously collected feature data with different coordinate system-related properties. These workflow errors have existed since the early days of GNSS-driven GIS data collection; however, it is occurring more commonly with the adoption of high accuracy capable hardware and use in feature-first GIS workflows in lieu of position-first survey workflows, where rigorous geodetic handling is more common.

Trimble GIS software has always been coordinate system ‘aware’ and we are excited to be making significant improvements to our Trimble TerraFlex software in this area. In preparation for the release, we wanted to “set the stage” through a blog series:

  1. Coordinate Systems 101: The importance of geodetics for high-accuracy GIS data collection
    In this post, we’ll provide an overview of the fundamental concepts of geodetics necessary to understand why coordinate systems are so important to GIS.
     
  2. Common problems with coordinate system configurations, or, “Why does my data look that way?”
    Next, we’ll draw from our long history of helping customers solve coordinate system configuration issues in their data and workflows.
     
  3. What is Trimble doing to solve these problems?
    We’ll take a look at what we are doing to solve these problems in TerraFlex, the Trimble Connect Map Viewer, and Trimble Terra Office add-in for ArcMap.

Continue to Part 1:  Coordinate Systems 101: The importance of geodetics for high-accuracy GIS data collection