Latest Contributions by MelitaKennedy

‎10-03-2012

In 102100 and 3857, we can use an ellipsoid/spheroid-based geographic coordinate system because the map projection algorithm is handling the conversion to a sphere internally. 102100: PROJECTION["Mercator_Auxiliary_Sphere"] 102113: PROJECTION["Mercator"] This parameter: PARAMETER["Auxiliary_Sphere_Type",0.0] determines how an ellipsoid-based GCS should be handled in a map projection that supports spheres only. The zero value means to use the semimajor axis for the sphere's radius. "1": use semiminor axis, "2": calculate authalic sphere's radius, "3": calculate authalic sphere's radius and convert geodetic latitudes to authalic latitudes. With 102113 (3785), because the GCS was sphere-based, technically you would have to do a geographic (datum) transformation from WGS 1984 to the sphere-based GCS before the projection could occur. This is more difficult to handle because it means all data has to go through a geographic transformation. In 102100 (3857) only non-WGS84 data has to go through a geographic transformation. Both definitions give exactly the same results. Melita (edited to add sentence about results, 1:22pm PDT)

‎09-26-2012

Hi Joseph, Try wrapping the XML with CODE tags. If you have "standard editor" set, it's a hash (#) button. <ogc:Filter xmlns:ogc="http://www.opengis.net/ogc xmlns:gml="http://www.opengis.net/gml xmlns:wfs="http://www.opengis.net/wfs"> <ogc:DWithin><ogc:PropertyName>Polygon</ogc:PropertyName><gml:Point> <gml:pos>152.540349 -32.444276</gml:pos></gml:Point><ogc:Distance> ogc:units='m'>60000</ogc:Distance> </ogc:DWithin> </ogc:Filter> Or, this appears to work too, at least when previewing the post. In the "Additional Options", check on "Disable smilies in text". <ogc:Filter xmlns:ogc="http://www.opengis.net/ogc xmlns:gml="http://www.opengis.net/gml xmlns:wfs="http://www.opengis.net/wfs"> <ogc:DWithin><ogc:PropertyName>Polygon</ogc:PropertyName><gml:Point> <gml:pos>152.540349 -32.444276</gml:pos></gml:Point><ogc:Distance> ogc:units='m'>60000</ogc:Distance> </ogc:DWithin> </ogc:Filter> Hope this helps, Melita

‎09-26-2012

Hi Miguel, What happens if you change the data frame's coordinate system? I'm able to reproject a National Weather Service WFS from its native NAD83 to an Albers projection, for instance. Melita

‎09-24-2012

(some clipped...) Here is what I know about the raster file: gdalinfo: PROJCS["unnamed", [INDENT]GEOGCS["WGS 84", [INDENT]DATUM["WGS_1984", [INDENT]SPHEROID["WGS 84",6378137,298.2572235630016, [INDENT]AUTHORITY["EPSG","7030"]],[/INDENT] AUTHORITY["EPSG","6326"]],[/INDENT] PRIMEM["Greenwich",0], UNIT["degree",0.0174532925199433], AUTHORITY["EPSG","4326"]],[/INDENT] PROJECTION["Polar_Stereographic"], PARAMETER["latitude_of_origin",70], PARAMETER["central_meridian",-45], PARAMETER["scale_factor",1], PARAMETER["false_easting",0], PARAMETER["false_northing",0], UNIT["metre",1, Polar sterographic projection: Image size: (3060 X 3060) Elliptical Earth radius=6378.273000 (km) e2=0.006693883 Reference point: lon=-45.000000 , lat=70.000000 (deg) X,Y scales: lon=2.225000 , lat=2.225000 (km/pix) Lower-Left Corner: x=-3400.000000 , y=-3400.000000 (km/pix) I believe there are two issues with the definition. It's either being converted by ArcGIS to Stereographic_North_Pole or Stereographic, or nothing. What does ArcGIS say the coordinate system is? Anyway, I think it's being read as Stereographic, because the raster is centered at 45W, 70N. I think it should be centered at 45W, 90N, with a standard parallel at 70N. The other issue is the discrepancy in the ellipsoid/spheroid being used. These values: Elliptical Earth radius=6378.273000 (km) e2=0.006693883 are Hughes 1980. While we have a GCS for Hughes 1980, it's not a true geodetic datum/geographic coordinate system, so there are no transformations between it and WGS84. Anyway, we have this definition already, it's "NSIDC Sea Ice Polar Stereographic North" and can be found in the projected coordinate systems, polar folder. Try redefining the data to this. If you still see a north-south offset that gets worse the farther from the pole, try setting a custom geographic (datum) transformation between Hughes 1980 and WGS 1984. Use the geocentric translation method, and leave the parameter values set to zeroes. Perhaps try it in ArcMap first (access it from data frame properties, coordinate system tab, transformation button. EDIT: The coordinate system is not 100% NSIDC Sea Ice Polar Stereographic North. There's a false northing in the coordinate system of -6800000 meters. I'm attaching the coordinate system prj file that appears to work reasonably well. I have to rename it to a .txt file to upload it. Or when you redefine the coordinate system for the raster, choose the NSIDC one, then modify it to have a false northing = -6800000.0. Melita

‎09-19-2012

Hi Rachael, The points are in UTM zone 12 North, rather than 13 (very generally: Red Hill area of the county). Try defining the data as NAD 1983 UTM Zone 12N. At that point you can either let ArcMap project it on-the-fly to zone 13, or create a copy via ArcMap (right click in the table of contents, data, export data, choose to export in the data frame's coordinate system) or the Project Tool (once the points are in a shapefile or feature class). Hope this helps, Melita

‎09-19-2012

The only thing I can think of it that there's already a scale factor in a tranverse Mercator definition, unlike a (US) Lambert conformal conic one. It's applied like this in the algorithm: X (SPCS/UTM easting) = FE + sf*(x) Y (SPCS/UTM northing) = FN + sf*(y) where FE/FN is the SPCS/UTM false easting or false northing values sf = scale factor (0.9996 for UTM, 0.9999375 for NAD83 SPCS WY) x/y = the calculated values for the zone before the scale factor and false easting/northing are applied. So when I create a custom local coordinate system, if the grid-to-ground is applied to the final SPCS/UTM coords, the modified TM-based coordinate system will have both new false easting/northing and scale factor parameters. X (TM easting) = SF*(FE + sf*(x) ) Y (TM northing) = SF*(FN + sf*(y) ) SF = grid-to-ground new scale factor = SF*sf Melita

‎09-18-2012

Hi, We really need an example point from the CSV file, plus a general idea of what location the data represents (county, city, etc). Melita

‎09-18-2012

You should be able to read it directly. bil (band interleaved by line) is supported. The other files (.hdr, .blw) include info like the georeferencing. USGS readme is a little outdated. The section that says you may need to convert to GRID assumes that you're using ArcInfo Workstation. In ArcGIS Desktop, you can use the Raster to Other Format tool. You might need to use the Define Projection tool to set the coordinate system. You should check the individual data file's readme to see what it says. There's some information in readme that I included a link for above, but I seem to remember that it's out of date too. Melita

‎09-18-2012

Hi Fionn, I don't know of anything off-hand. There are some sea ice and other coordinate systems from NSIDC (EASE), but nothing that jumps out. Most are also equal area, not conformal. You may want to create a custom coordinate system using Lambert conformal conic. One rule of thumb for choosing the standard parallels is to set them at 1/6 and 5/6 of the north-south extent. Melita

‎09-18-2012

Hi, If you didn't, you need to unzip the file with 'use folder names' or something similar. Except for a .xml file, the other files are in two folders: mn30_grd info The grid file folder is mn30_grd but it also requires the info folder. The info folder contains files that have the attribute information. Always use ArcCatalog to move grids and coverages (and file geodatabases, etc) if you haven't use the formats before, as it's easy to miss a required file or folder. In ArcMap or ArcCatalog if you browse it the folder that contains the mn30_grd and info folders, you should see mn30_grd as an available raster. Hope this helps! Melita

‎09-17-2012

The map31 data is in decimal degrees. Use the Define Projection Tool to define the data with the appropriate geographic coordinate system. Then you can use the Project Tool (or ArcMap) to convert it to PSAD56 UTM 17South. It might be in PSAD56 or WGS84. Melita

‎09-10-2012

Current NAD83 and WGS84 data can generally no be considered coincident. They're getting farther apart with time because of how they are being maintained. NAD83 and its re-adjustments are tied to the North American plate to try to minimize coordinate change over time. If your WGS84 coordinates were not post-processed or acquired while doing real-time processing, the accuracy is probably not enough to matter. If it was real-time or post-processed, it's likely that the coordinates are already in NAD83 (actually one of the re-adjustments) because the control points used are already on NAD83. Geomofo - As of 10.1, ST_Transform can support geographic (datum) transformations when working with Oracle. The functionality hasn't been ported to the other DBMS yet.

‎09-06-2012

It sounds like they're in the GRID format. If you're selecting at the .adf level, you're down too far. See Esri Grid format I think there should be an "info" folder also. If that's missing that could be what's causing the problem.

‎09-06-2012

...<text snipped> Doesn't v10.1 have a built in utility to track edits and who made them? I hadn't heard about this, so I looked it up. Search for "editor tracking" in the 10.1 help system. In the table of contents, it's located in Editing, Fundamentals of Editing, Editor Tracking. It has to be enabled and the information is stored in the attribute table. Here are the attributes: The name of the user who created it. The date and time it was created. The name of the user who edited it. The date and time it was last edited. Melita

‎09-05-2012

Hi Bali, I wasn't able to reproduce this in 10.1, but coincidentally, Jamal Numan had a similar problem in the general ArcGIS forum. Greg Keith noticed that the column header had a trailing space. Once the original person removed the space, no more null entries when the table was imported/viewed. Maybe check for starting or ending spaces, illegal character in the column names, etc? Melita

My Ideas

Latest Contributions by MelitaKennedy

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