Latest Contributions by MelitaKennedy

‎09-05-2012

There's a little bit of information in this help topic: Equation-based methods

‎09-05-2012

... I have gotten some points to draw, but seemingly not in the right place and with decimal degrees displaying in the scale window as well as at the bottom of the page... I'm not sure based on what you wrote, but are the original coordinates in decimal degrees but you want to use a different coordinate system? You'll need to convert these points to either an xy event table or a feature class in its native coordinate system first. Then project the data to whatever coordinate system you want to use. If you're using an event table, define the coordinate system of the event table with the data's current coordinate system. Then change the coordinate system of the data frame to what you want to use (including setting any geographic/datum transformation if necessary). Right click the layer in the table of contents and choose data, export data. In that dialog, set it to use the data frame's coordinate system. Hope this helps, Melita

‎08-27-2012

Hi Gabe, I'm wondering if this data is actually using a rotated world. Perhaps 59.2, -145.3 is the equivalent of the north pole, with -149.3 showing where the central meridian runs (which will be either north or south from the center point) and 60.1 is a standard parallel on the rotated world. Hmm, according to this tutorial: stand_lon = longitude/meridian parallel to the y-axis. truelat1,2 = standard parallels (2 is only used for lambert conformal conic) ref_lat, ref_lon = set the center of the displayed data Have you tried using Stereographic_North_Pole with: central meridian = -149.3 standard parallel 1 = 60.1 Do you have the sphere's radius value? Because that will throw off the calculations if you're using a standard GCS like WGS84. Melita

‎08-27-2012

Based on the 'look' of the raster, I think it was built in Albers, or possibly Lambert conformal conic, but we just don't know the parameters. You can try to georeference directly to geographic (pseudo-Plate Carree), but it's going to be worse. Georeferencing via world/header file is in a sense just overlaying a set of xy lines over the existing raster. If you look at how the longitude and latitude lines should overlay it, I think you'll see that they're angled or curved. Now you could import it with a start point of lat/lon and then use the georeferencing toolbar, but that's going to warp the data to fit the reference data that you use. Melita

‎08-24-2012

Has anyone seen excessive white space on the main forum page? In the sub-area 'box', there will be white space after the list of forums that's at least as large as the list. If I click between the columns and drag (like I'm selecting text), once I move the mouse into the white space, it'll disappear, but the other sub-areas may still show white space. A bit hard to explain, so I have some pictures below. I'm using IE8 (8.0.6001.18702) on winXP sp3. [ATTACH=CONFIG]17231[/ATTACH] and after click-and-drag: [ATTACH=CONFIG]17232[/ATTACH] I don't think I've seen it using IE9 on Win7 64bit. It's not a big deal; just odd.

‎08-24-2012

It's...reasonable. I don't know the data well enough to make a final judgment! Try changing these two lines: XLLCORNER 11421 YLLCORNER 275000 and then setting the data frame to USA Contiguous Albers Equal Area Conic USGS to check it out. Melita

‎08-24-2012

If you can post the lower left corner all corner coordinates, I can convert them to the Albers definition and look at the results. I would say try to convert it directly to lat/lon, but deciding on what the equivalent cell size would be in degrees is problematical! No possibility of asking the data provider for more information? Melita

‎08-24-2012

Where did you get the data? Is there any information there about the coordinate system or the data's lower left coordinates in any coordinate system? It looks closer to USA Contiguous Albers Equal Area Conic USGS (projected coordinate systems\continental\North America) but you'll need to figure out the coordinates for the lower left corner in that coordinate system. To see what I mean, add the converted raster and some reference data to ArcMap and set the data frame to USA Contiguous Albers Equal Area Conic USGS but modify (in 10.0, right click the name) it. Change these parameter values: false easting: 210000.0 false northing: 2600000.0 You can see that the coastline matches better than if you set the data frame to NAD 1983 UTM 15N (the closest match to some reference data). UTM shouldn't be used for this large an area. Melita

‎08-22-2012

Possibly this script: ET Generate 3.0 I'm not sure which version it was written for. Melita

‎08-20-2012

Hi Jayce, I'm sorry that I didn't respond sooner. You could use the South America Albers coordinate system or customize an Albers-based system for Brazil. The density of vertices is what's important. You don't want any long, two-point arcs (lines) as they won't be accurately represented when reprojected. Melita

‎08-20-2012

That's weird. It's definitely in my 10.0 version: vertical coordinate systems, North America. There are NGVD 1929 and NAVD 1988 plus another 4 definitions. Would you double-check please? Melita

‎07-10-2012

Hi, I'm sorry that I didn't reply sooner. Starting at version 10.0, there are pseudo-Lo definitions based on the Cape and Hartebeesthoek geographic coordinate systems (datums). One question is what datum this Zimbabwe data is using with the Lo definition. If it's Arc 1950, you would need to define a custom projected coordinate system that has the Lo projection parameters. If it's Cape or Hartebeesthoek, you can use one of the existing definitions, but will then need to reproject the data to Arc 1950 / UTM. There's no direct geographic (datum) transformation between Cape/Hartebeesthoek and Arc 1950. You could use a transformation for Cape or Hartebeesthoek to WGS 1984 and then one between Arc 1950 to WGS 1984 (use #9 for Zimbabwe). Melita

‎06-18-2012

Hi, I am trying to reproject a data set from the French system "RGF_1993_CC50" to the Belgian coordinate system "Belge_Lambert_1972" After doing so I noticed a slight shift against the BingMap basemap. I was able to reproject the data set in the Bluemarble Geographic Calculator successfully. After loading the reprojected data set into ArcGis the data and basemap matched perfectly. After comparing the parameters of ArcGis against these of BlueMarble I noticed that the transformation parameters are not available in ArcGis. I guess this is a bug ? How can I get ArcGis to make the correct transformation without having to create a custom transformation ? thanks, Jürgen We don't have any direct (one step) transformations between RGF 1993 and Belge 1972. It's possible to set up a 'path' (two-steps) of transformations using the Project tool, but not in ArcMap before 10.1. If you're using the Project Tool, which transformations are you using? Otherwise, if you want to project the data on-the-fly (in-memory) only in ArcMap and don't have ArcGIS 10.1 yet, you would have to use the Create Custom Geographic Transformation tool and concatenate the parameter values for two 3- or 7-parameter transformations. Melita

‎05-23-2012

Here's some of the important bits: PROJECTION["Transverse_Mercator"], PARAMETER["False_Easting",328083.3333333333], PARAMETER["False_Northing",820208.3333333333], PARAMETER["Central_Meridian",-85.66666666666667], PARAMETER["Scale_Factor",0.9999666666666667], PARAMETER["Latitude_Of_Origin",37.5], UNIT["Foot_US",0.30480060960121924] One thing to watch out for is that this definition is US survey foot-based. The false easting and northing parameters are also in US survey feet. When you implement the projection, the units are set by the unit of the semimajor axis of the ellipsoid (spheroid) so you'll need to convert it to US feet, or convert the results to US feet before adding the false easting and northing values. Melita

‎05-23-2012

Luke makes a good point. In a further clarification, how far off are the problematic datasets? It sounds like you may be using the data's property page or the Define Projection tool to change the coordinate systems. Is that correct? If so, that updates the metadata, but doesn't change the actual coordinate values. If the original datasets are actually in a projected coordinate system like a UTM or State Plane zone, the datasets after changed to WGS84 will show up wildly offset versus the 'good' data. If this is the case, use the Project Tool instead (and leave the original coordinate system as-is.). Melita

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