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Can anyone recommend a good reference or tutorial that explains the principles of spatial references, projections, and coordinate systems? We are a small team of programmers working with GIS technology, and we often get snagged when working with data in different SRS/CS because we don't understand the concepts.

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spatial referencing isn't for dummies :-) – WolfOdrade Apr 6 '12 at 16:08
Many of the answers to What strategies, criteria, or rules to use for selecting coordinate systems? also fit perfectly here. – matt wilkie Apr 10 '12 at 19:37
up vote 14 down vote accepted

Personally, for the cliff's notes I find the ESRI ArcGIS desktop software help system useful, and and also the ESRI book Understanding Map Projections, its first 30 pages are not unlike a short textbook, followed by ~70 pages of appendix on individual projections, their uses, strengths, weaknesses, etc.

From these, you'll quickly understand all the pieces of a complete SR - spheroid + datum + meridian + unit of measure => GCS; and projection + parameters + unit of measure + GCS => PCS.

For all the math, try the classic USGS Professional Paper 1395 by John P. Synder - Map Projections - A Working Manual. You might find a PDF somewhere if you google it.

Finally, take a look at the 'documentation' links at the bottom of the page for the Proj.4 library.

And as a DB of spatial references, I tend to refer to or another ESRI list provided as part of the docs for their ArcGIS Server REST API.

Hope that helps.

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The excellent USGS paper 1395 by John P. Synder is available at: (click on the View Document Link) – Devdatta Tengshe Apr 7 '12 at 3:28

Answering a question about the difference between a projection and a datum, Bill Huber links to his article in the Directions Magazine where he gives introductory explanations of georeferencing, datums, spheroids, and the like.

As short and concise as it can be!

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I think Carlos Furuti's tutorial is a really good resource.

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Furuti's work is truly exceptional. There are few who've managed to communicate complex ideas as accessibly and clearly. – matt wilkie Apr 10 '12 at 19:42

The PostGIS in action book has a great chapter, 6 - Spatial reference system considerations, on these subjects, although it is (of course) a bit targeted at PostGIS use. Well worth checking out.

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Hi Atlefren, welcome to :). We strive to collect and build answers that will give as much as possible in the moment of reading. In this particular instance that might mean including the name of the relevant chapter and perhaps linking to an online summary or preview (if such exists). – matt wilkie Apr 10 '12 at 19:49
Thanks for the pointers! The chapter i am referring to is chapter 6 "Spatial reference system considerations", other than the book website (which i linked to), i cannot find a summary or preview of this chapter) – atlefren Apr 11 '12 at 14:52

The OGP have lots of useful information on geodesy, try:

They also have a GIGS (Geospatial Integrity of GeoScience Software) program, more info here and also via OGP:

Hope it helps,


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I just ran across NOAA's "What is a Datum".

They seem to have more info on vertical datums than other sites I've seen.

(I guess data is no longer the plural form of datum.)

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Here's one for Arc that goes through several scenarios using vector data:

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