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DataDog
(Stranger )
06/04/07 10:24 AM
Scale and Resolution Report this article as Inappropriate to us !!!Login to Reply

I have a few questions about scale and resolution. If a dataset has a resolution of, say, 20 meters, can that information be (roughly) expressed as a scale? If a dataset is said to be mapped at 1:50,000 scale, can you then make a rough guess as to the resolution? I do understand where each comes from, etc., but I'm just not clear if there is a relationship that can be converted from one to the other even roughly. Anyone?



cplank
(Stranger )
06/05/07 11:47 AM
Re: Scale and Resolution new [re: DataDog]Report this article as Inappropriate to us !!!Login to Reply

The National Standard for Spatial Data Accuracy (http://www.fgdc.gov/standards/projects/FGDC-standards-projects/accuracy/part3/chapter3) defines the data accuracy. In your case, the statement would be that 95% of measured points are withing 20 meters of their true position. For printed maps, the National Map Accuracy Standard is used (http://rockyweb.cr.usgs.gov/nmpstds/nmas647.html). A 1:50,000 map can show data good to about 25.4 meters, or data appears within 25.4 meters of its true position (1/50 inch). By calculating backwords, the scale threshold for data with 20 meter accuracy would be about 1:39,370. Use of the data on larger scale maps would imply greater accuracy than supported by the data.





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