Posts Tagged “projection”
If you divide your time between ArcGIS and QGIS, you may have noticed that they don’t use the exact same projections. For Northern Colorado, for example, ArcGIS offers “NAD 1983 HARN StatePlane Colorado North FIPS 0501”, while the best QGIS can do is “NAD83(HARN) / Colorado North”. When projection information doesn’t agree exactly, I get […]
As a spatial professional, projections and geodesy have become second nature to me – often to a point that I take them for granted. In many cases, the projection becomes like a font in a presentation – if you used Helvetica on page one, you had better use it on page two. Generally, the consistency […]
PostGIS is a wonderful suite of tools, which really anchors the open source web mapping toolkit. However, it doesn’t always integrate well with an ArcGIS desktop environment. One obvious source of conflict relates to projections – most of ArcGIS’s projections are infinitesimally different than their real world counterparts. As an example, consider the Washington North […]
In my previous post, “When Scale Bars Lie”, I mentioned the dangerous things that can happen when the map unit is not set correctly. As I explained, it can lead to abnormal values, which are often manifested in scale bars. This week, a friend of mine was using GIS to calculate the areas of some […]
Occasionally, when knocking up a demo or a quick project in ArcGIS, you may find that your scale bar is lying to you. In the majority of cases, most GIS users don’t even take notice of their scale bars, much less question the veracity of the distances implied. However, if you have a projection or […]
