Latest Contributions by MelitaKennedy

‎01-12-2016

It's converting from NAD83 to WGS84, then WGS84 to ITRF2000. The 2nd transformation's parameters are zeroes. I call it a "bookkeeping" transformation. Even though the first transformation says WGS_1984_(ITRF00), it's between WGS84 and NAD83. The (ITRF00) is to clue that the WGS84 version is the approximately ITRF00 realization. Melita

‎01-11-2016

Is the data labeled with the different zones? Or do you have to graphically figure it out after adding it to a map? If the former, Dump all data into Excel (or other spreadsheet program). Sort by UTM zone Copy/paste one of the UTM zones data to another worksheet Delete that data from the first worksheet. Now use Add X/Y data on each worksheet. Possible alternative--use Convert Coordinate Notation to add geographic coordinates to the "table." If the latter, one possibility is to check what X coordinates are at the zonal boundaries in data's area. You may be able to sort the data using that information. Melita

‎01-08-2016

You would have to define a custom projected coordinate system in ArcGIS, but it's certainly do-able. Lambert azimuthal equal area has always supported non-polar cases in ArcGIS for Desktop, and did in Workstation too. Anyway, here's the well-known text string for the definition: PROJCS["raster_laz",GEOGCS["GCS_Sphere_ARC_INFO",DATUM["D_Sphere_ARC_INFO",SPHEROID["Sphere_ARC_INFO",6370997.0,0.0]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Lambert_Azimuthal_Equal_Area"],PARAMETER["False_Easting",0.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",-100.0],PARAMETER["Latitude_Of_Origin",45.0],UNIT["Meter",1.0]] Copy it as a single line to a text file, change the text file's extension to .prj, then you can import it through the raster's property page in ArcCatalog or the Define Projection tool. Your next question may be on what geographic/datum transformation should be used to convert to NAD83 or WGS84-based coordinate system (or to overlay it with that type of data). There's no predefined transformations between a sphere-based GCS and a geodetic GCS (AKA one based on a true geodetic datum). Try just adding the raster with your other data, ignore any transformation warnings. Does it appear to overlay? Then you're good to go. If it appears to be offset north-south, try adding a custom geographic transformation (there's a tool) between its GCS and NAD83 or WGS84 whatever you're using. Set the method to Geocentric Translation and leave the parameter values set to zeroes. Melita

‎01-08-2016

We do have some "named" realizations for NAD83 in the US - HARN, CORS96, NSRS2007, 2011. "NAD 1983" should only be used for the 1986 version, but some people use it for everything. When I can find an ITRF/NAD83 transformation from the NGS (National Geodetic Survey) CORS website, I put it, but also put "equivalents" where I include it for HARN and CORS96 or NSRS2007 and 2011, and possibly "1986." WGS84 is a generic definition. We've been debating adding the specifically named versions, but there's very little public information about how to convert between them. Also, what do we do with the existing "to WGS84" transformations? Do they apply also to any of the specific WGS84 realizations? Specifically for Alaska, I'm not sure I have a full solution for you. There was no HARN grid published to convert from NAD83 (1986) to NAD 1983 HARN that I'm aware of. GEOCON v2.0 will convert from the Alaska FBN re-adjustment of 1992 to NSRS2007 and then from NSRS2007 to 2011. That still leave a gap between 1986 and 1992. You might try contacting the NGS state advisor for Alaska to see what she recommends. Melita

User Conference Questions · ‎01-08-2016

It's uploaded. This should be a direct link to the powerpoint. The presenter also asked me to send his apologies for not uploading last summer. Melita

User Conference Questions · ‎01-07-2016

And, he said he's going to look into it (uploading the presentation).

User Conference Questions · ‎01-06-2016

I probably shouldn't throw my colleagues under the bus, but it's up to the presenters to upload the files either before/during/after the conference. We do get emailed (and reminded) several times to do so by the organizers. I've sent a note to one of the presenters asking about it. Melita

‎01-05-2016

Unfortunately, they didn't use GGRS87; it was defined after 1978. The map may have used the older Greek Grid, which uses a map projection that isn't supported in ArcGIS.

‎01-04-2016

They could be off for year-end holidays / university is shut. I would give it a week at least.

‎12-29-2015

The display xy data tool defaults the coordinate system to the whatever the data frame is using. If you have a base map loaded, that's usually EPSG:3857 aka Web Mercator. For data in a csv or text file, it's almost never Web Mercator but latitude/longitude values in degrees. I keep meaning to ask the mapping team about changing the default, or at least making it smarter, but haven't gotten around to it yet. When you open the display xy data tool, just change the coordinate system from the default to geographic coordinate systems, work, WGS 1984. Or when you click the Edit button on the coordinate system, type in 4326. Melita

‎12-29-2015

It looks like there's a related article here: Coordinates : A resource on positioning, navigation and beyond » Blog Archive » Improved algorithms for sailing calcu… The 2009 article is available for purchase. Otherwise, you could contact professor to see if he has a pre-print version that he would be willing to send to you. https://webacademic.snd.edu.gr/hydronav/Pallikaris/communicationEN.html

‎12-29-2015

Why not round the input value (internally) to the nearest 5 degrees, then calculate the way points?

‎12-29-2015

Showing up far to the west could mean an incorrectly identified coordinate system. For instance, the coordinates are in lat/lon but the definition is for UTM or State Plane. The "small" lat/lon coordinates would then show up southwest of true projected coordinates.

‎12-23-2015

HI Mark, You're right, you don't need that functionality. Please look at this topic instead: Available WMS service properties—Documentation (10.3 and 10.3.1) | ArcGIS for Server and search/scroll down to: Additional spatial reference systems You just need to list additional WKIDs in the properties so that they become part of the capabilities. Melita

‎12-21-2015

It's due to the fact that the CRS had an Esri number at 10.3.0, 103045, but was "code changed" at 10.3.1 to update the well-known ID to the EPSG one, 6463. They're just different numbers pointing at the same definition. Using the older number in a query that passes through the Esri projection engine, the older number is converted to the new one before use. I'm not sure what's occurring on the DBMS-side. Melita

My Ideas

Latest Contributions by MelitaKennedy

Re: Which version of NAD83 is assumed in geographic transformation?

Re: XY Table/Multiple UTM Zones to Single Feature Class

Re: Raster file missing spatial reference information

Re: Which version of NAD83 is assumed in geographic transformation?

Re: Online EUC Conference Proceedings (in)availability

Re: Online EUC Conference Proceedings (in)availability

Re: Online EUC Conference Proceedings (in)availability

Re: Getting real-world coordinates from a paper map with a custom projection

Re: geodetic sailing path.

Re: Shapefile not overlaying with other layers even though same projection

Re: geodetic sailing path.

Re: Great circle tracks

Re: Lining up CAD data - georeferencing

Re: Add EPSG:3857 as an additionally supported projection to a WMS service

Re: Feature Class SRID Not Matching Dataset in 10.3.1

Re: Append(merge,copy,..) two point Layers (GPS G...

UC 2026 presentations and more!

Re: New XY layer from Lat Long (DD) not plotting c...

Re: EPSG release and ArcGIS Projection Engine

Re: EPSG release and ArcGIS Projection Engine

Coordinate Reference Systems

Alaska GIS Users