Migrating Existing Geospatial Data to IMSMA Core
Migrating Geospatial data to IMSMA Core
When migrating from an earlier version of IMSMA to IMSMA Core, there are several considerations in relation to the geospatial coordinate storage for point, line and polygon data.
IMSMAng currently supports data entry in any Datum, with coordinates stored in the database as WGS1984 from a pure geometry perspective. This process of supporting data entry using other coordinate systems is still important, and IMSMA Core will attempt to follow the same patterns.
The GICHD recommends projecting all existing geospatial data from projected coordinate systems into WGS 1984 coordinates to provide central storage and a single geospatial coordinate format for all data. This one-time process is described in this document.
GICHD is aware of the long history and reasoning behind the use of local projections for data in IMSMA Core, but the following statement represents the decision to focus on WGS1984:
While there are important and historic reasons for using local datums, local projections or other reference systems, WGS 1984 provides a precise and functionally-equivalent representation of these features for the purposes of Mine Action.
For example – a difference in datum may lead to a coordinate being shown a few meters distant from another coordinate when establishing the boundary of an SHA. In reality, the boundary of the SHA should be marked on the ground and any technical survey team will likely cover the entire area, including the discrepancy in boundary. In this case is important to capture the relatively-precise size and location of the SHA, not capture SHA boundaries using DGPS which will then become irrelevant during the Technical Survey process.
Projecting Existing Geospatial Data
Any existing shapefiles, feature classes or other geospatial layers that are used in IMSMAng or are used by the Information Management team for other purposes should be consolidated as part of IMSMA Core development. WGS 1984 coordinate storage provides a precise and usable format for coordinates while ensuring that coordinate conversion, interoperability between applications and submission of data from the field are all kept in sync.
When projecting existing geospatial data, use the Project tool in ArcGIS Pro, and be sure to specify an appropriate translation for your data. For more guidance on selecting a translation for projecting data, see this page: https://blogs.esri.com/esri/arcgis/2009/05/06/about-geographic-transformations-and-how-to-choose-the-right-one/
It is recommended to project all data sources into a file geodatabase initially, and re-add the data to the map to ensure that boundaries line up and are equivalent to the pre-projection data. This review process will help to build confidence with the GIS and IM teams before loading the data to IMSMA Core’s PostgreSQL database.
Changing GPS Data Collection Procedures
The majority of Mine Action programs use advanced GPS data collection methods in the field to establish geospatial locations for devices, boundaries of hazardous areas, or EOD spot tasks. In many programs, these DGPS devices are set to record coordinates using a local datum and local projection. GICHD recommends that programs moving to IMSMA Core consider changing this data collection to use a pure WGS1984-based datum and decimal Latitude/Longitude coordinates. Digital storage systems for geospatial data already use decimal degrees WGS 1984, and setting field devices to use this datum will result in clean data collection and data storage workflows, while still retaining the necessary and useful level of precision that a Mine Action program may need.