THE_GEOM, THE_GEOM_WEBMERCATOR and map projections? What does this mean?
3 MIN INTERMEDIATE GEOMETRY, THE_GEOM, THE_GEOM_WEBMERCATOR, MAP PROJECTIONS
These columns are only added to your map when you have a data layer with either lines or polygons. When you add a point in your map, the Spotzi Mapbuilder only needs to add the Latitude (LAT) and Longitude (LNG) columns with the coordinates of that particular point.
When you add a line or polygon, THE_GEOM feature gives more information about the geometry. The geometry gives more information about the shape, size, relative position of figures, and the properties of space. All this data is stored in THE_GEOM.
This column is written in a different projection, called the Web Mercator. This projection was developed by Google in 2005 in order to make geographical data better editable for online purposes. This projection is based on the earlier Mercator projection. This projection is not only used to turn data from a globe visualization into a flat visualization as you know it from the Spotzi Mapbuilder, but this projection also allows you to quickly turn data into pixels on the map. In order to make this even faster, this location data is pre-stored in THE_GEOM_WEBMERCATOR column. Remember that THE_GEOM_WEBMERCATOR value is automatically edited once you change the geometry of the line or the polygon.
What is a projection?
Maps are a flat visualization of a round globe. The conversion of a globe to a map view sounds quite simple, but there is actually a quite difficult process behind this easy process that converts data on a spherical globe to a format, that can be used with the flat, plane maps of the Spotzi Mapbuilder. This conversion is called a projection.
Wikipedia gives the following explanation of Map Projections: “Commonly, a map projection is a systematic transformation of the latitudes and longitudes of locations on the surface of a sphere or an ellipsoid into locations on a plane.”
There are lots of different projections available. In the Spotzi Mapbuilder, we use a single projection called WGS 1984 Web Mercator.
So what is the difference?
By doing these transformations and automatically adding THE_GEOM_WEBMERCATOR column, we make it really simple for you to manage and display your data without thinking much about projections. So THE_GEOM describes the geometry of a particular map feature and THE_GEOM_WEBMERCATOR is used to make sure that the geometry that is described in THE_GEOM can be made visual in the Spotzi Mapbuilder.
What projections (coordinate systems) does Spotzi support?
When importing a dataset, it is also important to upload a dataset with a map projection (or: coordinate system) that Spotzi supports. The coordinate systems that are officially supported *:
- WGS84 (EPSG 4326)
- Amersfoort RD New (EPSG 28992)
- The following coordinate system is not supported:
- (Google) Web Mercator (EPSG 3857)
* These are just the coordinate systems that are officially supported, but there are a lot of other coordinate systems that should work too. Do you happen to have a coordinate system that also works with our data mapping software? Please contact us and let us know.