mkennedy
  • Member for 11 years, 3 months
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Displaying coordinates and inputs as LatLon or LonLat?
40 votes

You should take a look at the ISO standard 6709. Here's the wikipedia entry: ISO 6709 The main item is that order should always be latitude longitude. Latitude comes before longitude [edit now ...

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Identifying Coordinate System of Shapefile when Unknown?
34 votes

I'm promoting comments by Mapperz and Brandon Copeland by adding an answer that uses their technique. If you have ArcGIS Desktop, add some reference data that covers the same area to ArcMap. This ...

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What makes a MXD file size larger and how to decrease its size?
Accepted answer
32 votes

I've seen similar complaints on the Esri discussion forums and a quick search turned up this thread. Some suggestions: Save a copy of the mxd Open the geoprocessing results window and delete the ...

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Do ArcGIS SpatialReference object factory codes correspond with EPSG numbers?
Accepted answer
30 votes

If an Esri well-known ID is below 32767, it corresponds to the EPSG ID. WKIDs that are 32767 or above are Esri-defined. Either the object isn't in the EPSG Geodetic Parameter Dataset yet, or it ...

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Computing UTM Zone from lat/long point
Accepted answer
21 votes

It's not that difficult, even if you handle the zones around Svalbard and Norway. Here's an example: ZoneNumber = floor((LongTemp + 180)/6) + 1; if( Lat >= 56.0 && Lat < 64.0 &&...

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Difference between datum and ellipsoid for geodetic coordinates?
Accepted answer
19 votes

No, a datum and ellipsoid are not equivalent. For a loose definition, think of the ellipsoid as defining size and shape. The datum then fixes that ellipsoid to the earth. NAD83 (various realizations) ...

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Is the term "Quantum GIS" trademarked?
18 votes

The phrase, "Quantum GIS", is not found in the US Trademark electronic search. Trademark status is not mentioned on the Quantum GIS website, nor is, a trademark symbol nor statement used in the ...

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How does ArcGIS determine which transformation to use when projecting on the fly?
Accepted answer
16 votes

Note/Disclaimer: I work for Esri. Prior to ArcGIS for Desktop 10.1 service pack 1 (10.1.1), we loaded one geographic/datum transformation in ArcMap: NAD_1927_To_NAD_1983_NADCON (using the conus grid ...

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ArcCatalog says spatial references don't match between feature dataset and feature class with same coordinate system?
16 votes

This is an explanation rather than an answer. We (Esri) do pretty strict testing of coordinate reference system names and values. The 'is equal' test will not return a fail when comparing 500000.00 ...

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Is there a standard for the specification of .prj files?
Accepted answer
15 votes

There's some information on the OGC Call for Comments page on the new specification for coordinate reference system WKT standard. The original specification was written by Esri many moons ago for ...

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How to Dock ArcMap's Table of Contents?
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15 votes

After your grab the TOC, you should see a translucent blue rectangle that represents the new location of the TOC. Drag your cursor over to the left arrow/chevron (either one). The translucent ...

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Upgrading guidelines for ArcGIS Desktop?
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15 votes

You must uninstall a previous version of ArcGIS software before installing a new one. In fact, the install programs will require it. In addition, I suggest that if you have any Esri or 3rd party tools ...

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What is ArcSDE API used for?
Accepted answer
14 votes

The ArcSDE APIs date from the earliest days of ArcSDE. It was how you interacted with the data stored in a RDBMS. This was before there were ArcToolbox tools or many ArcObjects classes and methods. ...

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Arcpy Parallel Processing Environment
Accepted answer
12 votes

New at 10.1 SP1, from what I can find. This is not a complete answer, but a quick search of fixed "bugs" revealed references to mosaic datasets and geostatistical analyst tools. The latter has a ...

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Identifying Coordinate System of Shapefile when Unknown?
12 votes

Seriously outdated at this point, but Werner Flacke and Birgit Klaus posted Find Projection on ArcScripts in 2007. I don't think the source code is there, unfortunately. It's VBA-based so only usable ...

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How would I convert this point to WKID 4326?
11 votes

The coordinates appear to be in NAD 1983 State Plane Massachusetts (Mainland), in meters. I decided this by first adding state and county boundary data to ArcMap. They are in NAD 1983. I then checked ...

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How does a Spatial Reference System like WGS84 have an elipsoid and a geoid?
10 votes

WGS84 is natively XYZ, like the International Terrestrial Reference Frames (ITRF), and you can use an ellipsoid model to convert to latitude, longitude, and ellipsoidal height. Ellipsoidal heights ...

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How are ESRI WKT projections different from OGC WKT projections?
9 votes

You've caught a lot of the differences. Esri never adopted the WKIDs for the map projection algorithms or parameter names so those are all different. We didn't agree with how carefully defined the ...

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Huge differences between results for 7-param datum transform
Accepted answer
9 votes

First, Proj4 uses what EPSG calls the "Position Vector" version of the 7 parameter method. It's possible that GeoTrans and Leica GeoOffice use the other version which EPSG called "Coordinate Frame". ...

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2011 ESRI DevSummit
Accepted answer
9 votes

Remember that technical sessions are videotaped and posted after the conference if you're having trouble deciding between two. If a presentation will be repeated, it will be on Thursday afternoon. ...

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How does ArcGIS compute the distance between two points with a non-equidistant projection?
9 votes

In ArcGIS 10, check out IGeometryServer2 which now has GetDistanceGeodesic (geodesic distance between two geometries), GetLengthsGeodesic (return the geodesic lengths of each polyline), and ...

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Coordinate system for Finland in ArcGIS Desktop?
8 votes

As you found, EUREF-FIN is a realization of ETRS89 in Finland. Some countries, when displaying coordinates or transmitting data, use the convention northing, easting order while other countries use ...

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What's this PROJ4 string in WKT?
Accepted answer
8 votes

Technically, I think you have two questions. The first is just what's the WKT for this PROJ.4 string. The second is about how a CRS WKT is structured. An answer to the second question is probably too ...

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Identifying coordinate system for Jersey
Accepted answer
8 votes

Whoever thought this was ED50 UTM Zone 30 North was incorrect. The values instead match ETRS 1989 / Jersey TM, EPSG: 3109. Esri's version: ETRS_1989_Jersey_Transverse_Mercator WKID: 3109 Authority:...

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Spherical Mercator projection invented by Google and not conformal?
Accepted answer
8 votes

The Mercator projection has been around for a few hundred years. I don't know when the ellipsoidal version of the algorithm came into being (I don't have my reference books at my current location), ...

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What is the history behind WKT and proj.4?
Accepted answer
7 votes

Wikipedia's proj.4 entry has some information. Gerald (Jerry) Evenden wrote the original proj software to convert coordinates with a command-line interface. It focused on map projections so you were ...

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Vertical Datum and Projection
7 votes

No, when doing a map projection, the vertical coordinates are unaffected. If you look at the math behind a map projection (cf. Snyder's Map Projections: A Working Manual). you'll see that there's no ...

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What SRID is this?
Accepted answer
7 votes

There could be two possibilities. If the coordinates are in km and is the top of a ridgeline/mountain (approximately lat:46.853795 lon:7.985557), the CRS could be CH1903 / LV03, EPSG::21781. If the ...

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Does transforming to a new projection, then back, affect data accuracy?
7 votes

Esri has its own projection engine. Most projections and geographic/datum transformations methods are well-behaved when used in an appropriate area of interest. If you get too far outside of a UTM ...

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PROJ4 / PostGIS transformations between WGS84 and NAD83 transformations in Alaska
Accepted answer
7 votes

PROJ.4 uses the position vector method for its 7 parameter transformations. The ArcGIS transformation that you're referring to uses the coordinate frame method. They use different conventions for the ...

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