Latest Contributions by MelitaKennedy

I don't know if this will solve your problem, but here are the corresponding values for Nord Sahara 1959 Voirol Unifie Nord. A quick way to find these values is to pull the WKT from the .prj file. In version 10, it's located in the ArcGIS installation folder, Coordinate Systems, Projected Coordinate Systems, National Grids, Africa. For the other values, create a feature class in ArcCatalog using the coordinate system. You can then check the xy/z/m domains, tolerance, and resolution (1/Scale) values. XYScale = 1/XY Resolution. Thus, if the default XY resolution is 0.0001, the XYScale is 10000. <SpatialReference xsi:type="esri:GeographicCoordinateSystem"><WKT>PROJCS["Nord_Sahara_1959_Voirol_Unifie_Nord",GEOGCS["GCS_Nord_Sahara_1959",DATUM["D_Nord_Sahara_1959",SPHEROID["Clarke_1880_RGS",6378249.145,293.465]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Lambert_Conformal_Conic"],PARAMETER["False_Easting",500135.0],PARAMETER["False_Northing",300090.0],PARAMETER["Central_Meridian",2.7],PARAMETER["Standard_Parallel_1",36.0],PARAMETER["Scale_Factor",0.999625544],PARAMETER["Latitude_Of_Origin",36.0],UNIT["Meter",1.0],AUTHORITY["EPSG",30791]]</WKT> <XOrigin>-37094500</XOrigin> <YOrigin>-28508600</YOrigin> <XYScale>10000</XYScale> <ZOrigin>-100000</ZOrigin> <ZScale>10000</ZScale> <MOrigin>-100000</MOrigin> <MScale>10000</MScale> <XYTolerance>0.001</XYTolerance> <ZTolerance>0.001</ZTolerance> <MTolerance>0.001</MTolerance> <HighPrecision>true</HighPrecision> Melita ... View more

Those coordinates are web Mercator (aux sphere). You should set the xy data's coordinate system to WGS 1984 Web Mercator (Auxiliary Sphere). Are you seeing decimal degree values in ArcMap's status bar? You can change that by setting the display units. The setting is in the data frame properties, general tab. Melita ... View more

Hi Nathan, ArcGIS doesn't support a geographic coordinate system with a rotated pole. We have one projection, Krovak oblique conic, which defines a new pole as part of the projection parameters, but that's not what you need. It might be possible to use a custom datum transformation. The coordinate frame (7 parameter) transformation method works in XYZ space and supports 3 rotations. I need to discuss this with a developer. What sphere or ellipsoid model is being used? That will affect the transformation values. Edit: Actually it won't affect the transformation values per se, but the results. I'm now getting values that are in the right quadrant, but not matching some test points that I found. They may just be incorrect because I'm using WGS84 instead of a sphere. Can you identify some positions that I can use to verify my results? Thanks, Melita ... View more

Oops! Sorry about that. I was at home and didn't have access to check. We have added the coordinate systems for 10.1 (to be released next year). Melita ... View more

We added PNG94 in version 10, I believe. There's a transformation, but it has zeroes for the parameter values. According to the EPSG online registry, when PNG94 was defined, it was considered equivalent to the current version of WGS84. Both EPSG (I'm on the subcommittee that maintains the dataset/registry) and Esri add what people ask us to add. PCGIAP only lists PNG94, and no transformation information. There is an email contact for the National Mapping Bureau. Perhaps they might have some more information? I wish I could be of more help. Melita ... View more

Hello, I think you should take a look at the listings in technical article 21327 which lists areas of use and accuracy in the ArcGIS 10 version, and parameter values in the earlier versions. None of these transformations are listed as valid for Papua New Guinea. _2 is designed for ACT _3 is designed for Tasmania _4 is designed for NSW AGD_1966_To_GDA_1994_7 might be possible because it's for the Northern Territory, but we don't provide that grid file. Its information is included in the national version used in AGD_1966_To_GDA_1994_11_NTv2. This NTv2 transformation does extend to -10 latitude (only), but that doesn't guarantee that the values are reasonable. I've come across grids that 'smooth' out to the edges. Melita ... View more

It's currently marked as verified for 10.1 beta 2. It isn't marked as a service pack candidate, but that may not have been done yet (I think there's a 10.0 sp4 in the planning stages). A keyword if you haven't called yet: it's an equivalency issue. That is, it got broken at version 10. Melita ... View more

Hello! A transformation is always defined in a certain direction. All supported transformation methods (algorithms) are inversible. The software will apply a transformation correctly no matter which direction it should be applied. Melita ... View more

No, you wouldn't be able to make any projected coordinate system with "degrees" as the linear unit, unless you made a custom unit. In equidistant cylindrical, for a equal-length box of degree intervals (like 10x10), the north-south distance should be larger than the east-west. I wonder if the data is in pseudo-plate carree. That is, it is in decimal degrees and should be defined with a geographic coordinate system, which are being treated as if they're linear. Melita ... View more

Right-click the mouse to the right of the existing toolbars. That will bring up a context menu that lists all toolbars. Visible ones will be checked. Check on the Draw toolbar. It will be appear near where you clicked. If you have to, you can then click-and-hold to drag it around. The easiest place to click-and-hold for me is at the left of the toolbar. The cursor will change to 4 arrows. Melita ... View more

Hi Al, A little background! Please feel free to ignore it. We tried to change terminology in ArcGIS to make it more precise. "Projection" doesn't make sense if the data's in lat/lon, so we use geographic coordinate system (which includes a datum, angular unit, etc), projected coordinate system (includes a geographic coord sys, map projection, parameters, linear unit), and vertical coordinate system (must be defined in connection with a geographic/projected coord sys). The Define Projection tool or a data's property page in ArcCatalog let you define its coordinate system. Both methods update the metadata only--it doesn't change the data's extent or coordinate values. The Projection Tool (hate the name) will create a copy of a dataset, in the target coordinate system. The source data must already have its coordinate system defined (and it must be correct!). Many, many people make the mistake of using the Define Projection tool when they want the Project tool. I'm unable to reproduce your import problem. I'm trying it through the data's property page in ArcCatalog, XY coordinate system tab. All that happens is that the coordinate system definition is changed, nothing else about the shapefile. Beyond the Albers data, you have some NAD83 data that you're trying to project in a different coordinate system? Are they in lat/lon, rather than a projected coordinate system? I've attached a prj file for the NAD83 Albers definition. You'll need to rename the extension from .txt to .prj (I can't upload .prj) and place it in the coordinate systems, projected coordinate systems folder of the ArcGIS installation. Melita ... View more

When I open tools the tool page is blank of every tool. Ideas? I already repaired, and updated. Nothing changed You may want to post this query in the geoprocessing forum. This forum is for ArcInfo Workstation, which mainly runs from the command line. Unless you're using ArcTools (not the same as ArcToolbox/geoprocessing)! Running a search on 'arctoolbox blank' (without the quotes) turned up several forum posts with suggestions if you're using 9.3. 1. Downgrade IE from 8 to 7. 2. Rename the ESRI folder in the registry to ESRI_old (under HKEY_CURRENT_USER/Software/ESRI) which will force the keys to be recreated. 3. Got the correct XML files installed from http://support.microsoft.com/kb/324460 ... didn't work. 4. Deleted Normal.mxt, renamed ArcToolbox.dat. Neither helped. Melita ... View more

For a projected coordinate system (pcs), you can go directly to IProjectedCoordinateSystem::CoordinateUnit which returns ILinearUnit. You can then get its MetersPerUnit value from ILinearUnit. Similarly with a gcs, but now CoordinateUnit returns IAngularUnit with RadiansPerUnit. Starting at ArcGIS 10, you can calculate the geodesic length with IPolycurveGeodetic::LengthGeodetic. This is a 2D (well, on the spheroid/ellipsoid surface) calculation. We don't yet support geodesic distance calculations that include heights. I know the 3D team calculates a conversion value when horizontal coordsys is geographic to match up with the z values. It helps that data is usually large scale, so you can make an assumption. A rough equivalency is that 1 deg north-south is about 110 km. However, this only holds east-west at the equator. A rough estimate for east-west is 110 km * cos(latitude). Thus, at 60N or 60S, a degree is around 55 km. How the 3D team balances that out, I don't know. Melita ... View more

Hi Clinton, When you converted to Web Mercator Aux Sphere, what transformation did you use between NAD27 and WGS84? Is the data in the lower 48 states, Alaska, Hawaii, or Canada? (Each has a 'best' transformation) Thanks, Melita ... View more

Hi Al, ArcGIS doesn't support this definition. You should be able to 'import' the definition from your other data, otherwise, you'll have to create a new one, or modify an existing one. Modify is easier than creating a new one. Look in the projected coordinate systems, Continental and use one of the US Albers definitions. By the way, is this definition a statewide coordinate system for Oklahoma? Is it government-sanctioned? If so, I'd like to add it. Any website you can point me to? Melita ... View more