Latest Contributions by MelitaKennedy

I am creating a map that will show radio coverage of up to 45 kilometers (buffer zone) range around particular towns in Mali, West Africa. I want to then do a clip to pull out all of the villages within the buffer zone ranges in order to calculate the total number of population in radio reception range. What would be the best projection to use keeping in mind my location and also the purpose of the map? Thanks in advance! Hello, If you're using 9.3 or 10, and you're buffering points, keep the point data in a geographic coordinate system. The geoprocessing buffer tool will then create 'geodetic'-based buffers. That is, the distances will be unaffected by being in a projected coordinate system. Melita ... View more

As expected this issue returned after I installed the Desktop part of the ArcGIS 10 (Desktop, Engine, Server) Raster Format patch from http://resources.arcgis.com/content/patches-and-service-packs?fa=viewPatch&PID=17&MetaID=1648 I left ArcMap 10 open while editing the registry but had to then close and re-open ArcMap before seeing the workaround take effect. Anyone know an NIM bug number for this that we can use to track when it is fixed? - Graeme Hi Graeme, Possibly, NIM060238. However, its description says that upon using multiple ECW files (selecting a bunch of different rasters in ArcCatalog, not all are ecw), sooner or later the "invalid raster" error occurs. Close ArcMap/ArcCatalog and the files can be read again. The ECW displays upside down issue is NIM059863. Melita ... View more

I am searching for a method that can take any set of geographic coordinates (world-wide) that constitue a polygon (stored in a pointCollection) with a defined geographic coordinate system (datum, ellipsoid etc) and calculate the Geodetic Surface Area in square metres based on the ellipsoid. I imagine that somewhere within ArcObjects suite this must exist, and would be very grateful to anyone who could point me in the right direction. Thanks. No, that functionality doesn't existing within ArcObjects. Methods are generally approximations and we've been comparing some of them this summer. You'll get reasonable answers just by projecting the polygon to an equal area projection, hopefully centered somewhere near the data. If necessarily, you may want to densify the polygon first. At 10, you can now write code to densify a polygon or polyline with points on a geodesic, loxodrome/rhumb line, great elliptic, or normal section: IPolycurve4 or IPolycurveGeodetic. Melita ... View more

Hello, Does anyone know wich is the best geographic transformation to convert a raster from GCS_WGS_84to to ED_1950_UTM_Zone_32N? Thank you very much, Alessandro What is the data's extent? Or, what area are you interested in? If you have ArcGIS Desktop, look in the documentation folder and open the geographic_transformations.pdf file. Or it's here online: http://resources.arcgis.com/content/kbase?fa=articleShow&d=21327 Don't worry about the direction of a transformation. Generally, transformation convert from a older or local geographic coordinate system to a newer or more general coordinate system. Currently, all transformation can be applied in either direction and the software will handle it for you. Melita ... View more

Melita. I can transform individual coords via Grid inQuest's GUI; in fact I did this manually for a small set of coords, appended the results to my original spreadsheet, created XY feature from this set, added to ArcMap and they plot exactly where I want them to. It's the conversion of Batch Coords that doesn't work for me. Set attached. Couldn't attach a .csv here, so added an .xls Thanks. Hi Marc, Hmmm, the only problem I hit is that the setup for a batch file with lat/lon input wants ellipsoidal heights. I set it to use the ID column! Here's what I got: 200265.66997,733823.81832,-53.716,Newlyn 200300.70257,733781.28443,-52.715,Newlyn 200310.16479,733829.14868,-51.715,Newlyn 200332.75046,733828.08217,-50.715,Newlyn 200337.75582,733868.72512,-49.715,Newlyn 200355.59868,733832.57778,-48.715,Newlyn 200364.98978,733813.55384,-47.715,Newlyn 200387.63967,733792.04441,-46.715,Newlyn 200412.40735,733749.99721,-45.714,Newlyn 200877.60236,733402.89597,-44.710,Newlyn 200931.57506,733194.10461,-43.710,Newlyn 201175.05237,733338.73290,-42.708,Newlyn 201152.79377,733324.91487,-41.708,Newlyn 201178.09471,733293.99534,-40.708,Newlyn 201187.59682,733299.12297,-39.708,Newlyn Here are my steps. I'm using v6.6.0 build 1313. File, Convert files. Select the excel file. (Text File Decoding Wizard starts) Click Next to use New Format. On Select Rows to Decode, I set it to row 2. Next. Coordinate Format: Geodetic. Next. Select Data Fields:    Right click column 1 and select ellipsoidal height    R-click 2 and select latitude    R-click 3 and select longitude    Next Geodetic Information: coordinate format: Projected (Eastings, Northings)    (make sure it lists OSGB36 (OSTN02) in the projection section) Output File: I specified a text file, output.txt. Next. File format successfully defined. Finish the tool... I hope this is helpful, Melita ... View more

Hi. I'm hoping someone will entertain this query and apologies if it's been done to death. I have a set of GPS coordinates - points near the coastline. I want to tranform them to British National Grid (BNG) so I can display against some raster mapping of land. 1. My initial solution was to take the spreadsheet of coords, convert from degrees/decimal minutes to decimal degrees. Then use the Convert (files) function of Grid inQuest to transform from ETRS89 to BNG. Then create XY data. However, individual conversions work in Grid inQuest but every time I use the Convert (files) my results never produce a list in BNG. 2. I'm also attempting to use the Project function from Toolbox, however the Geographic Transformation option does not provide the tranformation I want, ETRS89 to BNG/OSGB36. Thanks. ESRI doesn't have the same transformation that the Grid InQuest tool does: OSTN02 and variants. You could use one of our OSGB_1936_To_WGS_1984_xx ones, but we don't have any for OSGB36 / ETRS89. I have the software but haven't tried using files with it. Can you post a sample row or two here? If your data is offshore, there's a possibility that Grid InQuest is treating it as out-of-range. I ran into that when working with the Irish grid file support. Can you convert one of those points via the GUI? Melita ... View more

There are many map projections that leave the Pacific Ocean intact as one piece, you simply need to reproject your data. In ArcCatalog is easiest... use the toolbox and select Data Management Tools >> Transformations and Projections >> Feature >> Project.  Select >> Projected Coordinate Systems >> World; now select your desired projection... Here are a couple of projections that are "Pacific-centric" (in a manner of speaking) and which you choose depends on your purpose: Robinson Miller cylindrical You can learn about others here http://webhelp.esri.com/arcgisdesktop/9.3/index.cfm?TopicName=List_of_supported_map_projections We have one western Pacific-centered projection, WGS 1984 PDC Mercator, suitable for small scale use in 10. Its center is 150E. The existing "world" projections supplied are all centered at 0 longitude (except World from Space). For any, you'll need to "modify" the existing definition and change the central meridian or longitude of center. You don't have to immediately reproject your data either. You may want to add some of your data to ArcMap, and then change the data frame's coordinate system. That way you can look at the results and keep modifying the coordinate system until you're happy with it. Regards, Melita ... View more

Hi, I need to do an analysis of an area somewhere in Madagascar. I do not have extensive data to start the analysis, but I have a map in a pdf format. The map shows a grid that is divided well enough that I can pinpoint every degree of latitude and longitude. I will need to add elements on the map to do my analysis and require precise location. These elements are defined in WGS84. So here is the problem. I created a shapefile of points for every lat and long of an area on the map, and imported it in ArcMap 9.2 I saved the pdf file in a TIF format and imported it in ArcMap 9.2 for georeferencing. When I start to georeference the map with the points, the result is not bad but far from being precise. I tried to georeference each latlong with the points but it is a disaster. Perhaps the grid on the map is not perfectly divided or I can't stretch the map properly ? (Perhaps it is the user?) The map does not tell the projection or coordinate system which doesn't help. Something I find funny, is that if I use the ruler to calculate the distance between each degree of latitude, I get 59.75 NM where it should be 60 NM. These are the points from the shapefile in WGS84. Does not make sense to me. By the way, I never installed the service packs for 9.2, and will get ArcGIS 10 soon. Don't know if this will make a difference. Thanks for any help I can get. The measure tool could be measuring the geodesic distance. I've noticed the same issue--there's a certain point where adding more control points doesn't help the least squares fit (in the georeferencing). The map could be using the Laborde projection which is the national standard. We didn't support until version 10. You might trying converting a few points to Laborde and georeferencing to them. Melita ... View more

No, I am looking for transformation from NAD1983 to NWS84 (Radius 6370 km spheroid). Ah, I haven't heard of NWS84. There are no transformations from a geodetic datum-based geographic coordinate system to a sphere-based geographic coordinate system. We do have a GCS already built with a radius of 6370000 m. It's called "Sphere EMEP". There's a geoprocessing / ArcToolbox tool called Create Custom Geographic Transformation. Use NAD 1983 for the input/from and Sphere EMEP for the output/to. For the method, if you have version 10, use Null. If you have 9.3.1, use Longitude_Rotation. If you do the conversion and the data is offset strictly north-south by kilometers, define a second transformation. This time use Geocentric_Translation for the method and leave the parameter values set to zeroes, and see if that works better. Melita ... View more

What transformation method will be best suited to convert the datum from NAD83 to NWS84? Do you mean WGS84 also known as WGS 1984? Try NAD_1983_To_WGS_1984_5. If the data is in the lower 48 states (except maybe the west coast states) and accuracy is a meter or more, try NAD_1983_To_WGS_1984. Regards, Melita ... View more

I have a map layer of facility locations (points) in the Lambert Conformal Conic projection.  I used the buffer tool to place a 3 mile buffer around each facility.  I also have a layer of census block centroids that is in the same projection.  I intersected the buffers with the census blocks to determine which blocks are within 3 mi of a facility.  This worked fine.  Next, I took the census blocks that are within 3 mi of a facility and projected from Lambert to UTM zone 10 (facilities are in Washington state).  Within the UTM coordinate system, I see that some of the census blocks that were barely within the 3 mile buffer in Lambert are now just outside of it.  For example, in Lambert one census block was 2.999 miles from the facility, but in UTM 10 it is 3.18 miles away.  I know there differences in the projections and perhaps the datums, but this seems like a big error.  Did I do something wrong?  What kind of differences should I see between Lambert Conformal and UTM in the western part of the U.S.? Thanks Hi Steve, I'm not really surprised, and there are several things that could affect this. Neither projection maintains distances. They're both conformal which maintain shapes. A UTM zone is designed to have distortions no worse than 1 part in 2500: thus the 0.9996 scale factor parameter. It also depends on the parameter settings in the Lambert conformal conic projection. The data may be in a different location relative to the projection's standard lines (where scale is 1.0) than when using UTM. Another problem may be due to the Buffer tool creating a circle with circular arcs rather than a densified polygon. When projecting a circular arc, we maintain it as a circle. It's possible that the buffer would change more if it was composed of densified points. Melita ... View more

I'm aware that going from arcgis -> illustrator is quite common. But I have the inverse problem. I have some vectors in illustrator that I want to open in arcgis. I tried to save in various autocad options but not once did they appear in arcgis, even though I checked the autocad layers and all the vector points were there. Here are the files. pdf http://docs.google.com/leaf?id=0B9wNtQ9NGRHuNmExYzA2NzEtOWZlYS00ZDViLTk2OTgtNDY4ZWE5YTNiZmUz&hl=en&authkey=COa3y7gC ai http://docs.google.com/uc?id=0B9wNtQ9NGRHuNmVkMjZjZWEtMTc2Ny00NDE3LTgxNmMtNTk0NTliMDA0OTFi&export=download&authkey=CIHK_5gE&hl=en svg http://docs.google.com/uc?id=0B9wNtQ9NGRHuMGRhYjQ1NDAtMzk5MS00ZDQ1LWIzYWUtM2E2NjM1OGRiODhj&export=download&authkey=CLyKoc0I&hl=en If someone can tell me why the autocad import doesn't work that would be really helpful. Thanks When you convert the features, are the coordinates in a particular coordinate system? If so, maybe you just need to define the coordinate system (so ArcMap knows how to overlay the data). Or you may need to georeference (if raster/CAD) or spatially adjust if vector the data. Melita ... View more

I have a DWG with these notes: 1. All coordinates are ground & adjusted to NADCON, +- 12 to 18 cm. 2. NAD 1983, NAVD 1988 3. Combine Factor = 0.99969305 4. Benchmark used NGS J-432, Published Elevation 5129.15 5. NM State Plane, Western Region I want to bring the file in to an existing ArcMap project where the Data Frame coordinate system is NM State Plane West NAD 1983 feet. I have tried to transform the file by adjusting the scale under the layer's Transformations tab but the points aren't moving where I know they should be located. Specifically, I click the Enable Transformations check box, click the Rotate, Scale, Translate radio button, and enter values of 0.99969305 or 1.00030695 in the Scale box. (I have tried both numbers.) What am I doing wrong? I've done it in ArcMap before but it's been a few years and obviously I am missing something. Aaron Allen Albuquerque, NM Hi Aaron, btw, when I inverse your scale values, I'm not matching. My calculator reports 1/0.99969305 is 1.00030704 while 1/1.00030695 is 0.99969314. Anyway, another way is to incorporate the combined scale factor (CSF) into a custom projected coordinate system. What you'll need is the CSF that converts to ground. You multiple the false easting, false northing, and scale factor values by the CSF to create new projection parameter values. Thus, the new pcs reflects the 'ground' coordinate system. I would suggest modifying the pcs name to reflect that the parameters are adjusted. Melita :cool: Read this section if you're interested in the math: When a projection is done the final values are calculated by: X_grid = false easting + sf*(bunch o'math) Y_grid = false northing + sf*(bunch o'math) where the other projection spheroid parameters are used to calculate the 'base' XY values. A CSF is applied to the final values: X_ground = CSF*X_grid Y_ground = CSF*Y_grid substituting in: X_ground = CSF*(false easting + sf*(bunch o'math)) Y_ground = CSF*(false northing + sf*(bunch o'math)) or X_ground = CSF*false easting + CSF*sf*(bunch o'math) Y_ground = CSF*false northing + CSF*sf*(bunch o'math) So we get: new false easting = CSF*false easting new false northing = CSF*false northing new scale factor = CSF*sf ... View more

Would anyone have a clue as to why it is that when I publish a map with the WGS 1984 Web Mercator (Auxiliary Sphere) the WKID is defined as 3857. In the help docs it states that it should be 102100 but I can never get my map services to show up that way. Further looking at the WGS 1984 Web Mercator (Auxiliary Sphere) prj file shows it is defined as 3857, so how does any one else get 102100 to show in the REST page? Even if I manually change the code in the prj I cannot get it to say 102100. Does anyone else have this issue? Running AGS 10 ADV ENT. The WKID was changed at version 10 to 3857. This is because this version of "web Mercator" closely aligns with the EPSG dataset's entry (http://www.epsg.org). Doc's out-of-date, I'll ask that it be updated. The multiple codes are due to release timings: A. 102113 (because that was the only way we could emulate the web services' definition) B. 102100 added next, using a differently built, but *completely* equivalent, definition C. EPSG then added 3857 (and deprecated their earlier 3587 entry which was closer to how 102113 was defined) D. We changed the ESRI 102100 code to EPSG 3857. Melita ... View more

Hey Derek- your link sends me to a place called salesforce.com; is this where we need to go and then sign up for a free 30 day trial?  Seems kind of odd... I had the same problem when the Ideas site was first opened. Try http://ideas.arcgis.com instead. Melita ... View more