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SEDAC User Feedback and Frequently Asked Questions (FAQs)

Need help with SEDAC data or services?  We suggest first searching our FAQs using the box at right.  If you don't find the answer to your question there use the "Contact support" link below the search box to get in touch with SEDAC User Services.  We are available Monday through Friday, 9 a.m. - 5 p.m. U.S. Eastern Time, with the exception of major U.S. holidays.

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Knowledge Base

  1. GPWv4 →

    1. When will the new GPW be released?
    2. Why are there negative numbers in the Population Density files(GPW V4.11)?
    3. How is a global raster created from tabular census data and boundaries?
    4. NetCDF questions and population density data
    5. I would like to use your density of population to study climate impact and how affect society. In particular, the doubt is from density of population in Africa. I am extracting the .nc file from Panoply in txt and it gave me 20 raster. The question is what raster corresponds to the 2020 year?

  2. Global Roads →

    1. Why was gROADS developed?

  3. Climate Effects on Food Supply →

    1. Are extreme events considered in the model?
    2. Are farmers' capacity to adapt to climate change included in the model?
    3. How should I interpret the yield changes? Expanded question: Let's take an example of India where wheat production is projected to decline by '- 2897341.18' tonnes by 2020 compared to 1990 production (ActChWHA1F2020). Since India produced '49850000' tonnes of wheat in 1990, according to this database it is likely to produce 46952658.8 tonnes ('49850000' - '2897341.18') in 2020. Since India produced '80,680,000' tonnes of wheat in 2009-10, the projected decline in 2020 is likely be 42% of the 2009-10 production. I understand that these numbers are not meant to be taken literally and are just indicative in nature. However, I want to know if I am correct in my interpretations.
    4. What is the main strength of the data?
    5. What types of crops were included in the study?

  4. Air Quality Data for Health-Related Applications →

    1. Do you know what part of the grid the latitude and longitude associated with each grid represent? Do these coordinate points represent the center of each grid or one of the corners?
    2. Do the RDS data sets (which are matched to these points) contain different information from the raster grids (GeoTiff?).
    3. Latitude and Longitude of gridded dataset

  5. Hazards Mapper and HazPop App →

    1. Where is aerosol optical depth on the app?

  6. Anthropogenic Biomes →

    1. I was excited to see you have anthropogenic biome data, which would be useful in my research. What are the differences between the Anthropogenic Biomes of the World, v1 data and the Anthropogenic Biomes of the World, v2 data for 2000?

  7. Mapping & GIS →

    1. I want to visualize/mashup many of your Web Map Services in ArcGIS Online, or even ArcMap. But, I'm not having much luck with ArcGIS. Is there some guidance you can provide to help me here. I'm sure I'm not alone with this request and as ArcGIS Online is becoming more proliferate other will want to leverage your great services themselves in their own mashups.
    2. We have downloaded the population estimate data for France (frap05ag.asc). When we use this file to calculate population for a given polygon, it does not match the response returned by the Population Estimation Service provided. We were wondering what is your criteria for including a grid cell in the calculation? Are you giving weight to a cell based on polygon intersection area? Also, wanted to clarify the xll, yll corner values - do the values -6, 40 represent the center of the bottom left cell or do they represent bottom left corner of the bottom left cell?
    3. How do I open ArcInfo Interchange file (.e00) in ArcGIS?

  8. Poverty Mapping →

    1. On the "Prevalence of Child Malnutrition" data set using the 1/4 degree raster file called "UW", the values for the visualized raster data ranges from near 0 to over 500. But this does not make sense, because according to the documentation and the readme file, the "UW" file is supposed to represent the percent of children under age 5 who are malnutritioned. By that definition the values should only range from 0-100.

  9. User Registration →

    1. What is the User Registration System and why do I have to register?
    2. Is the information I provide to the URS safe?
    3. Where can I learn more about user registration?

  10. West Africa Coastal Vulnerability →

    1. Will SEDAC develop other similar regional collections?

  11. About SEDAC →

    1. I looked at your website and I am very interested in working for SEDAC. How do I apply for a job there?
    2. What is SEDAC?

  12. Archive of Census Related Products →

    1. How can I access the 1980 and 1990 Census, STF3a files?
    2. I am trying to locate maps online of the Metropolitan Statistical Areas (MSAs) for all US states and Puerto Rico and haven't had much luck. Can you tell me where I might find these maps?
    3. I have downloaded some of SEDAC's 1980 census tract boundary files in "BNA" format, but am unable to read them in Arc GIS 8.1. I was told that there should be a conversion program "bna2shp.exe" somewhere on your site but am unable to find it.
    4. I was interested in obtaining a Geographic Correspondence file, particularly Block Group to Block, for every state, containing allocation factors for Population, Land Area & Housing Units. Is it possible to obtain these .csv files directly from you?
    5. I'm working with the 1980 PUMS. I just want to make sure I understand the coding of age. Does the age variable refer to the person's age on Dec 31, 1980. If not, what exactly does it measure?

  13. ENTRI →

    1. What happened to ENTRI?

  14. China Dimensions →

    1. Do you have the China maps available that are subdivided at the prefecture level for 1995? I have seen the county level ones on your website but these are too detailed for my purposes.
    2. Hello! I want to know in what unit is the field ‘Area’ in the China Admin ArcInfo file?
    3. I am a graduate student. I am interested in all the chinese information and maps at your website and trying to design a small project for my class. But I find there are no information about the map projection. The administrative Region map projection is different from that of the Fundamental Maps.
    4. I am trying to find China's Agenda 21 policy document. Do you have it on your web site?
    5. 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?

  15. Environmental Sustainability Index →

    1. Could you please let me know if there is any link between the ESI and Corporate Triple Bottom Line (TBL) Reporting? Alternatively, would you regard the ESI as a proxy for national TBL reporting?
    2. Could you please tell me how and with what kind of weighting the ecological footprint has been factored into the 2002 ESI?
    3. How often will the ESI be updated?
    4. I am currently evaluating different indices of sustainable development and came across the 2002 ESI profile for Belgium (Annex 5, p. 93). Could you explain why air quality is above average when the emission of air pollutants ('reducing air pollution') is extremely high?
    5. I am looking for the ESI reports for 2003 and 2004.   Is the ESI available for these years?

  16. GPW →

    1. I have imported the country-specific population density grid maps in ArcGIS for Argentina, Mexico and Honduras. I'm trying to join a table of points by latitude/longitude to these maps and export a table with all the data. The problem I'm having is that there does not seem to be any geographic data even though the maps are projected with WGS1984 correctly. I downloaded it from the site in the .bil format.
    2. I am using the GPW data (version 3) for China and I have some problems with understanding the proportional allocation mechanism. The reason that I am asking is that there are so many zeroes and I can not understand how there can be any zero?
    3. How do I convert .BIL format in Arcview/ArcInfo?
    4. How do I get GPW data into GRASS?
    5. How should I cite the GPW3 data?

  17. GUPPD →

    1. Can I request the data in a GIS compatible format? What about regional level data?

  18. GRUMP →

    1. After extracting all the data from GRUMP and adding up population by country to get country population totals, should the totals add up to match exactly the totals reported in the country summary?
    2. Are the quadrilaterals formed by the meridians and parallels of the Urban/Rural Area grids proportional to the area on the globe?
    3. 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.
    4. 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.
    5. 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?

  19. Discussion Lists →

    1. How do I unsubscribe from this list?
    2. I'm new to the list, is there any way I can see old messages/threads that were posted to the list.
    3. Where can I find help in using the commands associated with this list?

  20. Gridded Species Distribution →

    1. What are family richness grids?
    2. I see you have data on mammals and amphibians, do you also have richness grids for bird species?
    3. How is SEDAC’s Gridded Species data different than the IUCN Red List?
    4. What year(s) is this data from?
    5. What are the species grids maps about?

  21. Last of the Wild →

    1. Exactly how is the Human Footprint Value calculated? I need to know how the normalization was performed.
    2. For which part of the earth's land surface is the human footprint data available?
    3. How is the Composite map of the Human Influence Index performed (0-64)?
    4. Since the footprint data uses the spheroid GRS1980, can I just define it as NAD1983? I know that NAD1983 uses GRS1980, but I am not sure if I can define this layer as datum-based instead of spheroid-based.
    5. What is the Human Footprint Index?

  22. Low Elevation Coastal Zone (LECZ) →

    1. I see you have country-level estimates for the low elevation coastal zone data. Is it possible to get the gridded data?

  23. Metadata →

    1. How often is the CIESIN Geospatial Metadata Writer's Guide updated?
    2. I am having difficulties locating the metadata for your population density data of the world, GPWv3. Is the metadata available online?
    3. What version of the FGDC Metadata Standard does SEDAC use?

  24. Miscellaneous Questions →

    1. I am participating in a research study and am in need of population density maps for select countries in Africa and Asia. Can your organization provide me with such maps?
    2. I'm preparing an article about "human migration and environment". Do you have any data or information relevant to this topic (causes, effects, links)?
    3. What is the projection that the Census use for its ArcInfo files?

  25. Permissions →

    1. How do I get permission to reprint a GPW map?

  26. Population Landscape and Climate Estimates →

    1. When I open a CSV file in excel, there are special characters that do not display correctly, what do I do?
    2. Can PLACE I, PLACE II, and PLACE III country values be compared directly?
    3. Can the PLACE I and PLACE II country values be compared directly?
    4. What is the difference between PLACE I and PLACE II?
    5. What is the difference between PLACE II and PLACE III?

  27. Georeferenced Population of Mexico →

    1. 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.
    2. I am working on a map of Mexico that details population dynamics at the state level and am wondering if you have such information (e.g., total fertility rate, natural increase, inward and outward migration), or if you have a suggestion as to who I might contact.
    3. I need to use the GIS coverage of Mexican States in some of my current institutional projects. I did the download from your site, but I don't have ArcInfo in my PC and I know that all the files are in ArcInfo export format. I was trying to open the files from ArcView, but it was not possible. Do you know if this information is also available in some Arc/view format?

  28. Thematic Guides →

    1. I am in the process of developing a new interactive desertification website. I have found your website by surfing the web and have found it a wonderful site that I would like to refer a link to. In addition I would like permission to enter some articles that are on your site onto our site.

  29. Environmental Performance Index →

    1. Where is the EPI from 2019/2017/2015/2013/etc. ?
    2. Can I assemble the releases of the EPI into a time series or panel dataset?
    3. Are there any EPI reports before the 2006 EPI? What is the difference between the Pilot 2002 EPI and the Pilot 2006 EPI?
    4. Regarding the EPI 2010. Could you clarify if the EPI scores can be, in fact, taken as a percentage (%).
    5. What is the reason that an EPI was established as a complement to the ESI?

  30. All articles →

    1. I looked at your website and I am very interested in working for SEDAC. How do I apply for a job there?
    2. Do you have the China maps available that are subdivided at the prefecture level for 1995? I have seen the county level ones on your website but these are too detailed for my purposes.
    3. Are extreme events considered in the model?
    4. How do I unsubscribe from this list?
    5. Could you please let me know if there is any link between the ESI and Corporate Triple Bottom Line (TBL) Reporting? Alternatively, would you regard the ESI as a proxy for national TBL reporting?
    186 articles →

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