GPW and GRUMP

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  1. Are the quadrilaterals formed by the meridians and parallels of the Urban/Rural Area grids proportional to the area on the globe?

  2. How big is the file (.ascii) of GRUMP data? I am downloading from a very fast connection and it is still taking a really long time.

  3. How do I convert .BIL format in Arcview/ArcInfo?

  4. How should I cite the GPW3 and GRUMP data?

  5. I am attempting to download and use your 1990 Adjusted Population Numbers for Africa. I have successfully downloaded the zipped BIL file. In order to convert this for use in my GIS software (I am using IDRISI) I need to know information which I cannot find in any of the documentation files you have made accessible. Please can you answer the following questions regarding the BIL format: 1. Is there a header - if so what is its size? 2. What are the maximum and minimum grid co-ordinates for your Africa data? 3. Are the data 8-bit or 16-bit? 4. What reference system do you use, and what the reference units measured in?

  6. I am having difficulties locating the metadata for your population density data of the world, GPWv3. Is the metadata available online?

  7. I am looking for gridded population data and elevation data on the same grid. I saw on your website that you have compiled a population dataset - is there an elevation dataset that can go with this, and can you help me obtain it?

  8. I am looking for the population and the surface area (in square kilometers) for several cities throughout the globe.  I found several datasets available in GRUMP, but I didn't find anything with both population and surface area.

  9. I am slightly confused as to what is meant by "urban extent" and "settlement points" - please could you send me a definition? Also, I have found the global map which shows "urban extent" - which I guess is the areas of the Earth's surface which are covered by urban areas. I am wondering if you, or anyone else you know of, has a time-series of such maps, showing how urban coverage has changed over time?

  10. I am trying to get population densities for world metropolitan areas (e.g., # of residents per square kilometer or square mile) and if possible comparison figures for previously points in time (e.g., the latest available estimate versus 1 year ago, 5 years ago, etc.).  Can I use the GRUMP data ?

  11. I am using the multibandread function in MATLAB to read in the glds95agi15.bil file I downloaded from CIESIN. I need help setting some of the input parameters for the function. * what is the height (rows), width (elements or columns), and depth (bands) of the file or how do I figure it out? * what is the number format? integer or float? how many bytes?

  12. I am very interested in the gridded population density data for Africa.The source for the maps you provide is cited as the UN, but having contacted them they are unsure of the data you have used to produce your maps.Is it possible to obtain these data from you, including population numbers for different regions of Africa as well as the density calculations that you have mapped?

  13. I compared GRUMP Alpha population grid and GPW v3 population grid for the year 2000 in 1° grid. I am surprised to see that there are some huge differences (the largest difference that I noticed is 8.77x106 people).  How do you explain these huge differences?

  14. I downloaded Asian Gridded Population data from your FTP site. These files are in E00 format. I converted these files into Mapinfo TAB format using universal translator that is tool of Mapinfo. But no map was present if I open these TAB files in the mapinfo. Only one record was present in the table with fields MIN, MAX, MEAN, STDV. How can i convert these files into mapinfo format.

  15. I downloaded the ArcInfo interchange files and tried (after import) to open them with the ARCGIS 8 software but each time it failed to open the file. I think the sta.adf file is missing (or another one). Could you please help me?

  16. I downloaded the global level data file v2glp95ag.zip I looked into the file content on a unix system using 'more', and found most grid values to be less than 1. This is unexpected, as I expected the number of inhabitants per cell. What did I do wrong?

  17. I downloaded the urban extents grid from GRUMP (alpha).  When opened in ArcGIS, there are only two values 1 and 2.  What do these values mean ?

  18. I have been trying to download the GRUMP/GPW datasets but the web download does not seem to be working.

  19. I have downloaded India 1995 population data (GPW2). Why is there no variation in colours when I view the files in ArcView?

  20. I have successfully downloaded the GPW global datasets for the years 1990, 1995 and 2000. I would like to know if it is advisable to compare datasets of different years in order to assess changes in population densities and therefore migration patterns, or if there are constraints that hinder such operation.

  21. I plan to use the global population data. I would like to know what information is stored in the *.stx and *.blw files. Also is there a way to map the grids to (latitude, longitude) ?

  22. I'm using population density data, 2.5' grid.  My question is -- If a small populated island is the only land in a given cell, and its area is smaller than the cell's, how is the population density for the cell computed?  Is the population of the island distributed over the whole cell's area?  Or is the population density of the island applied to the whole cell?

  23. In GPW data that is comprised of 2.5 arc min cells, are the cells georeferenced from the cell center, or right/left and upper/lower corner?  I understand that xllcorner and yllcorner give the starting lat/lon for overall grid position, but are the cell data themselves valued at each lower left corner?

  24. In GPWv3 Population Density Grid data, .ASCII format, what is the definition of "xllcorner" and "yllcorner" values?

  25. In the Urban extents data, how were the urban areas identified?

  26. In UN-adjusted 2000 density data, how is the data adjusted to match UN totals ? The Africa UN-adjusted map shows some significant chunks of zero density (e.g, much of Gabon) that don't seem realistic.

  27. In what formats are the data available?

  28. I downloaded your Population Grid maps for the United States and the World both at a resolution of 2.5 arc minutes, and I have a few questions. First, what are the units of the grid values? From what I've noticed, they run anywhere from the thousands to 1e-9, which seems kind of strange. Also, at the same resolution, why does the United States have more columns than the world?  The data at the top says there are 8688 columns at a cell size of 0.0416666, which would imply 362 longitudinal degrees of data.

  29. The maps on the GPW web site report population in the thousands.  Is this the same for the grid or is it unscaled?

  30. We are looking for a high-resolution gridded population data for our project.  It seems to us that compared to the GWP3 data, the GRUMP data offer a higher spatial detail and probably a more accurate spatial distribution of population.  Which would you recommend ?

  31. We have been using the GPW data extensively, but one question I cannot understand is why the data appear not to be available in database format rather than GIS format.

  32. What are the differences between GPW, GRUMP and Landscan?

  33. What are the restrictions on use and redissemination of data?

  34. What has happened to .e00 format option? It appears to have been replaced by something called "grid"?

  35. What is a .BIL image file format?

  36. What is the difference between "..ag"  and "...g" files?  For example, I've downloaded the population grid for the whole world for 1990, in "grid" format, and there are two sets of raster files.  When I open them in ArcGIS, they seem to show similar data, but the range of values for the raster is somewhat different: 0 to 1.24 million versus 1 to 1.17 million.

  37. What is the difference between GPW and GRUMP population grids?

  38. What is the projection used for the data?

  39. What is the spatial extent domain for the different file formats of 30" GRUMPv1 Urban Extent Grid?

  40. What years are the data available for?

  41. Where are the attribute tables for the GPWv3/GRUMP data? I would eventually like to extract statistics (such as population count) using features in another layer, but am not sure that I'll be able to do so given that there are no accompanying attribute tables. Could you advise as to how I should proceed?

  42. Why can't I make the Import71 work with the GPW data?

  43. Why is it that the total population of the settlement points is not equal to the country total population?

  44. Why is there a difference between the population estimates of UN and National Statistical Offices estimates?

  45.  Is the data symmetrical from the Equator?  In the ascii format using a 0.5 degree resolution, the yllcorner equals -58 degrees. Since there are 286 rows, this represents a total of 143 degrees. Is the upper left corner then at 85 degrees latitude (-58 + 143)?

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