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    1. What is the difference between the Population Count and the UNWPP-Adjusted Population Count data sets? And between the Population Density and the UNWPP-Adjusted Population Density data sets?

    2. What does a zero in the population density grid mean? What does No Data mean?

    3. Which are the last updated and the next scheduled GPW collected data?

    4. In GPWv3, what exactly does "No Data" (-9999) mean?

    5. For which part of the earth's land surface is the human footprint data available?

    6. I am looking for projection information for your Mexican Municipios data. I need to reproject the data and I need to know what the original projection was for the coverage.

    7. 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.

    8. Which ellipsoid / spheroid is the geographical data of the Fundamental GIS: Digital Chart of China based on?

    9. How is SEDAC’s Gridded Species data different than the IUCN Red List?

    10. 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?

    11. I see you have data on mammals and amphibians, do you also have richness grids for bird species?

    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. Where can I find land area data for 1990 census tracts? I am trying to determine the median square mileage of census tracts.

    14. 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?

    15. Do the RDS data sets (which are matched to these points) contain different information from the raster grids (GeoTiff?).

    16. I have a question regarding the data set Contours of China and the Surrounding Areas. What Surrounding Areas are included in the data? What is the difference between the contour.zip file and the contourp.zip?

    17. 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.

    18. 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) ?

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

    20. What is the projection used for the GPWv4 data?

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