Latest Contributions by MelitaKennedy

When you add other layers, for example Great Lakes, do your polygons fall where you expect them to, or do they get squished into a very small area? It sounds like you've got the wrong projection. By the way, feature classes in geodatabases automatically calculate the areas of your polygons. +1, particularly since you mentioned that you "redefined" the coordinate system. If you used the data property page in ArcCatalog or the Define Projection tool, you assigned a new coordinate system to the existing coordinate values. That would definitely explain the small area values you're getting--the coordinates are still in lat/lon. You need to redefine the data back to its GCS and then project it to the equal area projection. Melita ... View more

Please see response here. Please try to give at least a day for a response after posting a message before trying another forums. Thanks! Melita ... View more

Hi, I have a problem with a program called LaharZ. It runs with ArcGis but I can't find how to do it. Most of its files have the .aml extension. Someone can help me, please? Thank you Hi Leticia, The program(s) work in ArcInfo Workstation, not in ArcGIS Desktop. You need to have an ArcInfo license and install ArcInfo Workstation. You may also need a GRID or Spatial Analyst license. I didn't look closely at the PDF file that accompanying the programs to see. ArcInfo Workstation has a number of command-line driven programs such as ARC, ArcPlot, ArcEdit, and GRID. Melita ... View more

I want to georeference an SID Image file in ArcMap. I wish to use simple latitude and longitude to do so. Of the various predefined systems available in ArcGIS, which one do I use? If the MrSID file isn't already georeferenced, you should use what's appropriate for the data's area of interest, or what the rest of your data is using. Melita ... View more

Hello FetznerJ, It looks like the first layer should be using a geographic coordinate system, rather than a projected coordinate system. The extent values look like decimal degrees, particularly if the data is in southern Mississippi. Redefine it as NAD 1983 (don't reproject it) using the Define Projection tool or the data's property page in ArcCatalog. Melita ... View more

Rather than changing the SRTEXT, I change the SRID in layers and geometry_columns to match the coordref with the SRTEXT I'm trying to match. I haven't tried using a '-R' to work around this, but I doubt it would work. pe_coordsys_eq does a string comparison. - V pe_coordsys_eq does compare the names in the two coordinate systems, which are strings, but the objects are compared so that the number equivalency is easier to calculate. ... View more

When creating geodesic circles in ArcGIS 10, is there a reason why buffering from Point features results in a true geodesic representation, however buffering from a Polyline does not? I have been using the 'Buffer' geoprocessing tool only.  I noticed when buffering from a polyline, it did not appear to produce a true geodesic buffer.  When I used the 'Feature Vertice to Points' tool to convert the same polyline into points, I then conducted another buffer using the same 'buffer' tool.  This time it yielded a more accurate geodesic buffer. Why is this so?  Is it an algorithm problem? We haven't implemented geodesic buffering for polylines or polygons yet. The first bullet in the usage section of the Buffer Tool talks about when buffers will be geodesic-based. Buffer Tool help Melita ... View more

Hi Melita, This topic has been around for a while (see http://forums.esri.com/thread.asp?c=93&f=984&t=189688). Are there any news regarding geodetic area calculation in ArcObjects? Will the approximation methods be made available to developers? Best regards Fridjof Hi Fridjof, We have been working on it but it's a little early to state which software and/release it will be in. Melita ... View more

Dear Melita, Thank you for VBA sample, it did help us. While exploring this combination of transformations, we have spotted some problems. We are trying to do transformations from Gauss-Kruger to ETRS89 using combination of Helmert transformation of 7 parameters and custom grid-based transformation. Grid has cells of 1000x1000 meters, and covers entire territory of Serbia, is based on residuals from Helmert transformation, while for gridding method was used Inverse Distance to a Power, with radius of 10000 meters. Doing such transformations, we got results that differs from results we got using other software (non-GIS) that calculates transformations: 95% of coordinates were exact, whilst 5% were wrong (not satisfying standards of our client, since coordinates must have error not larger than 10 cm). By researching all the methods we have used, we spotted that NTV2 custom grid in ArcGIS is in arc-seconds. Is it possible to have custom NTV2 grid in Cartesian coordinates rather than in arc-seconds, in ArcGIS? Also, is there a tool that can convert grid from ASCII to GSB format in ArcGIS? Thank you in advance! Best regards, Vojkan Gajovic, GISDATA Belgrade Serbia Dear Vojkan, Unfortunately, the software is set up so that a 'geographic transformation' (datum transformation) must be between two geographic coordinate systems. Werner Flacke at ESRI-Germany wrote tools a few years ago (for 9.1 and 9.2) that could convert a shapefile to an NTv2 file (it's still in ArcScripts), but I don't believe the source code was released. There was a thread recently on the PROJ4 mailing about converting some Dutch information into an NTv2 file: http://lists.maptools.org/pipermail/proj/2011-April/thread.html#5634 It mentions that a recent version of GDAL now supports NTv2 as a format. Melita ... View more

Thank you! Am I supposed to mark this thread as answered or something? There's no way to do so. The Esri team that works with the forum software is working on adding that type of functionality. I supposed you could rate the thread high, but you don't need to. Melita ... View more

Hi, if I want to project a point from one SpatialReference to another SpatialReference with a different datum (using GeoTransforamtion), the Z-Coordinate should be changed. At IGeometry.Project(...) it is mentioned that "The Z and measure values are not changed by the Project method." But the IGeometry2.ProjectEx(...) doesn't work either. Is there any way other to project Geometries that I'm not aware of? Thanks Hello Thomas, We aren't yet doing any vertical (z) transformations, even when the input/output z values represent ellipsoid-based heights. We do plan to add this functionality, but it will be in a future release. Melita ... View more

Thank you for your time. I have used the prj-files successfully in other scenarios, thats my reason to believe they work. As cooIn I use the file "SWEREF99 TM.prj" and for cooOut "RT90 25 gon V.prj". I found them under (App-Folder)\"Coordinate Systems\Projected Coordinate Systems\National Grids\Sweden\" My test coordinates is: x = 7454204.638 y = 761811.242 The result (in RT90 25 gon V) should be: pnt.X = 7453389.762 pnt.Y = 1727060.905 I'm using ArcView 9.3.1 and ArcGIS Desktop SDK .NET 9.3.3000. Hello Roger, I may have an answer. You have to remember how US-centric ArcGIS is. In ArcGIS, x = easting = longitude y = northing = latitude Try swapping the x and y values and you should get a better results. ArcGIS usually doesn't apply any geographic (datum) transformations automatically. You may want to switch to using IGeometry::ProjectEx and set up a GeoTransformation. It looks like the code is 108212 for SWEREF99 to RT90 so you apply this with esriTransformForward. To create it, use ISpatialReferenceFactory::CreateGeoTransformation. Melita ... View more

I guess I didn't explain myself very well. I am trying to overlay proposed shovel test locations (I'm an archaeologist) on a project area in 30 meter intervals. Normally, I just create points by hand, but this project area requires more than 2000 shovel tests... the measured grid shows what I need, but I can't seem to convert the graphic so that I can delete extraneous points, and only show the "dots" in my project area... I know that there is an easier way, but can't seem to find one other than creating each stp point by hand.. How about the Create Fishnet tool? It creates a polyline or polygon feature class, but there's an option to create label points. If you use the polyline option with create label points, you'll get a point feature class. Melita ... View more

The code looks okay to me. Are both spatial references valid? What are they and what's a sample input point? What version are you using? Melita ... View more

Hello, I'm looking for insights on why the spatial reference of an IMG raster (it's big, that's why it's in IMG format) displays as 'NAD_1983_Albers' in ArcGIS 10 and 'USA_Contiguous_Albers_Equal_Area_Conic_USGS_version' in ArcGIS 9.3.1.  This inconsistency is present in Python SpatialReference objects (both arcpy and arcgisscripting flavors) and in the ArcMap Layer Properties GUI.  I can code around it, but it seems like a potential bug. Thanks, Lisa Hi Lisa, Esri stores coordinate system information by well-known ID (wkid aka "code" or EPSG code) and by well-known text (WKT). Sometimes Esri adds a coordinate system with a particular name, then EPSG, an external authority, adds the same definition with a different name. Each also has different wkids. When we can we will update an Esri entry to use the EPSG wkid because that's a more widely accepted authority. Rasters are more complicated than vector data because of the different formats. The coordinate system information is stored differently in the various file formats. In this case, possibly the wkt from 9.3.1 is mapping to the 10 wkid, which has a different wkt in the IMG format code! Melita ... View more