We are implementing a CMAPI 1.3.0 programming interface to abstract basic Gis commands from the actual Gis library underneath (Luciad Lightspeed 2016.0).

In the map.view.zoom command, I don't understand the meaning of the range parameter. I posted this message to the official discussion group. It's been a while now and nothing came out of it (yet). For those who can't read the question, I wanted to emphasis the following post:

Is there a formula for how "camera height above earth's surface" can be calculated from the map scale?

The closest I have found is this article (https://blogs.esri.com/esri/arcgis/2008/02/25/map-viewing-altitude/) that explains that "the altitude depends on the map’s scale and then on your viewing distance away from the center of the map". As it does not make sense have the definition of the map zoom depend on your current viewing distance from the screen, it would be nice if someone can clarify how the CMAPI zoom property relates to map scale.

Does anybody knows how to convert Map Scale to/from CMAPI range?


The description for the range parameter in the CMAPI map.view.zoom message was updated on May 9, 2016 to read:

The distance in meters from the map. For a 2D map this may be translated to the closest zoom level. For a 3D map it should be interpreted as the camera's distance in meters from the center of the map - which is essentially the camera's altitude when looking straight down.

According to this I interpret range to equal zoom level if 2D-map. They have not defined "zoom level", but most map engines use a int value from 0 and up. The Open Street Map wiki provides a overview of how to convert from zoom level to scale and/or resolution: http://wiki.openstreetmap.org/wiki/Slippy_map_tilenames#Resolution_and_Scale

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