In my last discussion I introduced the topic of the new GDA2020 datum, the reasons behind it and how Esri intends to implement support for this new geodetic datum. Now that the impending initial release of the first set of parameters is due shortly and with the NTv2 grid due before the end of the year, I thought it important, that as an organisation, it is time consider how do you go about planning the move to this new datum.
Well the first and most important thing I must say is don’t rush into migrating your data to this new datum when it becomes available. Take the time and consider what the implications are to your organisation and plan the migration. Treat it as major project because by no means is it going to be a simple undertaking.
Back in the year 2000 Geoscience Australia introduced the GDA94 datum. At this time there was a considerable amount of GIS data and imagery but compared to what we have today, with explosion of sensors and image formats it could be considered relatively small volume of data.
Today there is not just vector data that needs to be considered. Almost every organisation has multiple epochs of imagery as well as LiDAR and elevation datasets. Then there are information products based on these.
However, let’s take step back and look at this in detail.
First and perhaps the simplest is the map documents (ArcMap .mxd and ArcGIS Pro .pro files). The map documents can be seen as a tool to reproject data on the fly to the new datum and “see” how the datasets overlap.
Next is the vector data. Whether this be in an Enterprise Geodatabase, File Geodatabase, shape file, CAD file or another vector format they all will need to be reprojected. This means creating completely new datasets with the new datum. However, there may be dependencies such as topologies, geometric networks, routing networks and parcel fabrics which also need to be recreated or repointed to the new datasets.
Imagery, Elevation surfaces and LiDAR. Careful consideration will need to be given to these datasets as any reprojection will result in very large and lengthy processes, simply because raster data and LiDAR is large by nature. Perhaps consider if an on-the-fly reprojection is acceptable.
In all examples where data has been reprojected then map documents will need to be updated to point to the newly reprojected datasets. This then has a flow on effects for the web mapping environments. Web services are based on map documents, which will need to be updated. Also map and image caches will need to be recreated for the updated datasets and web services.
Are your maps and web applications in Portal for ArcGIS or ArcGIS Online in Web Mercator or a GDA94 projection? Which web services do they consume and do these need updating?
So you can see the migration is not going to be a simple undertaking. Take stock of all your datasets and information products and take the time to plan migration. At all stages test the results, test the outputs and make sure your data has migrated correctly. Treat the move to GDA2020 as a significant project that is going to affect your entire organisation and plan for the move. Geoscience Australia will release the GDA2020 parameters soon, Esri will incorporate these as soon a practically possible and only then can we map out the move.
Esri Australia is here to offer support to all our customers with this impending move. We can assist in assessments of your data, migration and scripting for the migration of your datasets and advice on the best paths forward.
All the best