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Latitude of scale in a stereographic projection

July 23 2009 | 0 comments
Categories: Map Elements

I have a data frame with a South Pole stereographic projection.

My question relates to the scale bars created by ArcMap. If I create a scale bar for this data frame, at which latitude is the scale true? At the pole itself, the center of the projection?  If I want to create a scale bar that will be accurate for a specific latitude (say -60), is this possible?


Mapping Center Answer:

My understanding is that scalebars derive the scale from the data frame, not from any particular location on the data frame. Data frames derive the scale from the full extent of the data, not from just the visible extent. So when you insert a scalebar, it reflects the scale of the data set itself. Specifically, it will reflect the scale at the latitude of the midpoint of the north-south extent of the data set. So if you have global data and are displaying it on a South Pole stereographic projection, it will reflect the scale at the Equator since that will be the latitude at the center of the data set. If you want to insert a scalebar that reflects the scale at -60, then you could create a "dummy" data set that extends from, for example, -30 to -90. Then you could add the data to a new data frame, turn off all the symbology so it does not show up on your map and insert the scale bar so that it is correct for that latitude.

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