![]() See Section 1.3 if you need to review how.ģ. In the Catalog pane, add a new folder connection to your GIS data folder. See Section 1.1 if you need a refresher on how to do this.Ģ. Open ArcGIS Pro and create a new map project. Figure 2.1: GPS waypoints, routes, and tracks (from Wikimedia Commons, authored by Berklas)ġ. Tracks are thus similar to breadcrumb trails, and can be transformed into vector line features by GIS software. For example, a GPS receiver might be programmed to record a trackpoint every 50 feet. Tracks are sequences of points called trackpoints, which are recorded automatically by the GPS receiver at regular intervals of time or distance. Routes are pre-defined paths created from waypoints or points of interest located from map software on the GPS receiver. Waypoints are point locations defined by a set of latitude, longitude, and altitude coordinates, along with a name and description given by the user. GPS receivers can record their position for later reference in three ways: as waypoints, routes, and tracks (Figure 2.1). For more information on how GPS works, visit the GPS.gov website. A GPS receiver captures orbital position and time information transmitted by four or more orbiting GPS satellites and uses this data to calculate its own geographic position in latitude, longitude, and altitude coordinates. GPS stands for Global Positioning System, and is a global navigation satellite system operated by the United States government that provides real-time position and time information anywhere on Earth. One of the easiest and most common ways to create new geospatial data is using a mobile GPS receiver unit. This means that it may take a while to download these files, and that you will need a fast PC to work with them.IMPORTANT! Before you begin this section, read the Chapter 2 Introduction and answer Teachback 1 on that page. High resolution files for large areas (countries) can be very large. A cell with a 30 seconds resolution is about 0.8 km2 at the equator and smaller at higher latitudes. The size in square meters varies with latitude. When the cell size is small (e.g., 30 seconds), resolution is high. ![]() The units are in (arc) degrees, minutes or seconds. The resolution is the size of each grid cell expressed as the length of one side of one (square) cell. For the other gridfiles, NODATA is only used for areas covered with water, except for the land cover grids, on which water is a separate class.Ī DBF (dBase file) is a dbase format database table. For these areas, the value is "NODATA" (indicating the absence of data for those cells). ( More info on format for developers).Ī gridfile with "country mask" indicates that the areas outside the selected country are masked out. From DIVA-GIS they can be exported to a number of other grid formats including IDRISI and Arc or to shapefiles. Shapefiles contain a single class of "vector" data such as points, lines, or polygons. It can be imported to most other GIS programs. This is a commonly used format that can be directly used in Arc-anything, DIVA-GIS, and many other programs. Grid (raster) data are stored as DIVA gridfilesĮach "shapefile" consist of at least three actual files. Vector data are stored as ESRI shapefiles You can use programs such as 7-zip, PKZIP or StuffIt to decompress the files. The files have been compressed and grouped in ZIP files. National Imagery and Mapping Agency's (NIMA) database of foreign geographic feature names They can also be used to map localities, however you can download more recent files from NIMA The files should be placed in the \gazet directory. The files you can download here are for use in DIVA for automatic georeferencing (to assign coordinates to places). Global gridded population databaseĪ gazetteer is a list of place names and their coordinates. Land cover, original data resampled onto a 30 seconds gridĬIESIN, 2000. Seperate files for line and area features The level of subdivision varies between countries Select and download free geographic (GIS) data for any country in the worldĬountry outlines and administrative subdivisions for all countries.
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