GIS data must accurately represent real-world locations to be useful. To do this, you need a standard framework for defining location – a coordinate system. All spatial data utilises a coordinate system to position itself relative to your map and other data. However, coordinate systems are frameworks. They are models, spheroids, imperfect approximations of the shape of the Earth with all its bumps and curves as it changes with time. When working with spatial data you need to consider how a GIS positions this data against reality using coordinate systems.
By better understanding coordinate systems, you will be able to manage your data in a way that increases the accuracy of your maps and the work that you do with them. This blog is the first in a series taking a closer look at using Australian spatial references in ArcGIS. We will start by looking at geographic coordinate systems, projections, and transformations.
It is now official on the 15th of December 2017 Geoscience Australia and the Intergovernmental Committee on Survey and Mapping (ICSM) launched the new GDA2020 datum.
In support of the new Australian datum, the following tools and resources have also been released by Geoscience Australia and ICSM:
So what does this mean for the ArcGIS product suite? Well from ArcGIS Pro 2.1 and ArcGIS 10.6 onwards all state, territory and national projections that incorporate the GDA2020 datum are supported.
NOTE: This article refers specifically to ArcGIS 10.6 and ArcGIS Pro 2.1. For later versions of software please install the ArcGIS_Coordinate_Systems_Data_Windows software available from My.Esri to obtain the latest NTv2 files.
Here are some of my favourite new tools and improvements that have come with the 10.1 release. These should make your mapping and workflows just that much more enjoyable.
1. Searching for a projection
With ArcMap shipping with over 4000 projections, it is easy to feel a bit overwhelmed, especially if you are a new user. Although you have always been able to save the frequently used projections to your favourites, you can now input keywords and find exactly what you are looking for. If you have no idea what you are looking for, you can even let ArcGIS use your current extent to suggest the best projection.
2.Enable Editor Tracking
Trying to figure out who moved that feature without telling you? Now with Editor Tracking enabled on your feature class, any new features or modifications will be logged with the username and time/date of creation or modification. This works with SDE databases as well. This is going to make your metadata housekeeping a lot easier. Note: This will not tell you if a feature has been deleted – best to use versioned geodatabases for that.