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# How to convert esri Units ?

1938
5
02-05-2018 05:39 AM
Occasional Contributor II

Hi,

We have line drawing Map tool using offset method (ex: wgs 1984 World Mercator spatialReference). But when we draw line in GeographicCoordinateSystem offset draws very huge (ex: TUREF spatialReference). How can we convert esri units for (when is Map in GeographicCoordinateSystem) draw small line ?

Here is ArcObjects code below:

IUnitConverter unitConverter = new UnitConverterClass();

private double offsetDistance ;

if (map.SpatialReference is IGeographicCoordinateSystem)
{
offsetDistance = unitConverter.ConvertUnits(WriteScalableDistanceTool.OffsetDistance, map.DistanceUnits, map.MapUnits);

}
else
{
offsetDistance = WriteScalableDistanceTool.OffsetDistance;
}

Thanks.

Tags (2)
5 Replies
MVP Emeritus

There is no 'fixed' conversion between Geographic coordinates (ie in decimal degrees) and planar units (ie meters, feet as from web Mercator projection).  You in essence have to 'project' your data to do the conversion and get your units in planar units.  So when you use a value of '2' as an offset, that is 2 degrees rather than 2 meters.  Work in projected coordinate space if you want to use planar units.

Occasional Contributor II

Hi Dan,

We are using also Geographic coordinates for draw the right and left offensive roads in our vehicles.Are there any formula for convert (How much is 1 meter in decimal degrees?) Planar units to Geographic coordinates ? Or are there any alternative way  to solve this problem ?

Thanks

MVP Emeritus

There is no such thing as how much is 1 meter in decimal degrees.  That  depends where on the surface of earth you are.  If can be determined via a 'projection' of the decimal degree data to a planar coordinate system... for instance a UTM projection for your area

Occasional Contributor II

Thank you for your reply, but I can not understand the sentence you wrote last.Can we solve this problem or can not solve it.

Thanks

MVP Emeritus

You need to 'project' your data http://pro.arcgis.com/en/pro-app/tool-reference/data-management/project.htm

every esri application has access to tools to project data... the above is the help topic for ArcGIS Pro