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location Redlands, CA
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visits member for 4 years, 7 months
seen 3 hours ago

I've been working with map projections and datum transformations for years, including in ArcView GIS, ArcInfo 7 and up, MapObjects, and ArcGIS.


10h
comment Transform from Lambert Azimuthal “old” to ETRS89_LAEA
Addendum: Once you have data on ED50 (rather than the sphere), you would use ED50 to WGS84 (1), EPSG:1133, to transform it to WGS84. Parameter values are -87,-98,-121.
10h
comment Transform from Lambert Azimuthal “old” to ETRS89_LAEA
ArcMap or QGIS? The input ellipsoid has a radius that's equal to the semimajor axis of International 1924 which is used for ED 1950. I would try unprojecting to lat/lon using R=6378388 first. Then redefine as ED50 and project to the other LAEA ProjCRS. But the error message says that it can't write using the raster format you chose. Does it work if you choose something else?
11h
comment How to project WRF data (lat/lon) onto ArcGIS maps
There are several WRF-related questions already. You might want to look at them to see if any apply. If the data is really lat/lon (in decimal degrees), it can't be in LCC. What coordinate system was assigned when the data was added to ArcMap? It might have defaulted to BNG, which would be incorrect.
1d
comment Why do GRASS' NC dataset and USGS' CONUS dataset coordinates disagree?
That's what I don't know. I've never used GRASS. If the NED imagery was being projected to NC state plane, and you do have the whole country, some of it should overlay the NC data. So, sorry, no idea.
1d
comment Why do GRASS' NC dataset and USGS' CONUS dataset coordinates disagree?
When I check all the NED datasets spatial metadata, they're all using NAD 1983, a geographic coordinate reference system (aka latitude-longitude in degrees). The Raleigh data looks like NAD 83 State Plane North Carolina in meters. Not sure why the NED data is showing 1.5 million.
1d
reviewed Close Displaying labels from join of annotation with polygon feature class?
1d
comment Can I use Redfearn's formula to convert between WGS84 and UTM?
GDA94 and WGS84 basically use the same ellipsoid (it certainly doesn't matter with the accuracy you have), so I certainly don't see any problem. (I'm an Esri projections specialist)
May
22
reviewed Approve GNSS planning online vs trimble planning 2.9 software
May
22
comment Best projection / CRS for short-distance based analysis?
If you're using software that doesn't support geodesic-based buffers but that's what you want, a work-around is to use an ellipsoidal azimuthal equidistant projection, centered on the point/feature to be buffered.
May
22
comment Best projection / CRS for short-distance based analysis?
UTM was designed to be no worse than 4 parts in 10000 or 0.4 meters in 1 km.
May
22
comment Best projection / CRS for short-distance based analysis?
Depending on which version you have, ArcGIS will calculate geodesic-based buffers for points, and probably for other feature types too.
May
22
comment R to ArcMap, erroneous change of spatial reference
You should be able to redefine the raster's coordinate system (spatial reference) as SWEREF99 TM again. What's showing in the warning is that the GCS has turned into an ellipsoid-based one, and the SWEREF99 information has been lost.
May
20
reviewed Looks OK geoExt2 application in a CMS (joomla, Wordpress)
May
20
revised How to use KML files with PhotoOverlay in Google Street View?
fixed klm typos
May
20
comment How to project WGS84 raster in lat/long to WGS84 UTM in ArcMap 10?
Did the Project Raster tool ask for a transformation? If it didn't, it's a weird, non-reproducible bug that keeps popping up. Instead, try reprojecting in ArcMap, set a transformation, then export the raster via data, export data (using the data frame's coordinate system).
May
19
reviewed Close how to export feature classes from geodatabase
May
19
comment Generate a series for each Survey_ID based on chainage sequence
Probably still needs further editing. I think the task is to use the increasing sequence in the chainage column and write a 1-based sequence in the last column, and restart whenever the chainage value decreases.
May
19
comment Table to ellipse not working properly
What happens if you change the spatial reference (coordinate system) to match the point_x/_y values?
May
19
revised Generate a series for each Survey_ID based on chainage sequence
reformatted text, small grammar changes
May
19
comment Table to ellipse not working properly
What are the values in the fields? If the point_x and point_y values aren't in decimal degrees, what coordinate system are they in?