San Diego Hydrogeology


Digital Elevation Model (DEM) Datasets Merged for the San Diego Hydrogeology Project

Multiple datasets for both land-surface elevation and ocean bathymetry were merged to create a single digital elevation model (DEM) that extends over the entire study area. This DEM has been used extensively throughout the San Diego Hydrogeology project to display data, to create geologic and hydrologic models, and to create illustrations for reports. Prior to creating this DEM, no single dataset was available that extended over the entire study area. Some datasets, such as Dartnell and others (2004), had detailed data, but covered a relatively small area; some datasets had less resolution, but covered a larger area. To be certain that the most detailed and accurate data were used to create the study area DEM, many datasets were compared, the metadata for these datasets were reviewed, and then the best datasets were selected and combined.

The datasets used to create the study area DEM are listed below, and were used in the order listed. The first dataset has the greatest detail and accuracy; the fifth dataset has the least detail and accuracy. To maintain the detail of the datasets covering most of the study area, a minimum resolution of 30-meter cell size was used. Datasets having a larger cell size were resampled to 30 meters.

  1. 2013 NOAA Coastal California TopoBathy Merge Project. This dataset provided 1-meter cell size raster data along the California coast, and was available as a bulk download at the specific projection needed for the study area. This dataset was used as much as possible to form the study area DEM.
  2. National Elevation Dataset 1/9 arc-second. This dataset provided 1/9 arc-second resolution, which at the San Diego latitude equates to approximately 3-meter cell size raster data. Because this dataset was available as 15-minute IMAGE raster blocks, a total of 31 individual, 15-minute blocks were merged together for 2 areas: the San Diego Bay and along the United States and Mexico border. Areas extending into the ocean were not used because the dataset included a default value of zero to indicate offshore areas. Further analysis indicated that the near-shore values were not as accurate as those in the 2013 NOAA Coastal California TopoBathy Merge Project dataset; therefore, all elevation values less than 2 meters (NAVD88) in the National Elevation Dataset were removed.
  3. San Diego, California Coastal Digital Elevation Model. This dataset provided 1/3 arc-second resolution, which equates to approximately 10-meter cell size raster data. This dataset is a well refined land and ocean elevation model that extends offshore and into Mexico, from a latitude of 33.6°N to 32.45°N, and from a longitude of 117.0°W to 117.5°W. This dataset was retrieved as one complete ASCII grid, which was then projected to the study datum and projection. This dataset was used to verify values of the 2013 NOAA Coastal California TopoBathy Merge Project. The bathymetric part of this dataset was composed primarily of the Southern California Coastal Relief Model (CRM) version 2, which was found to have errors near the offshore International Border; therefore, only data to a bathymetric depth of 10 meters (NAVD88) was used.
  4. National Elevation Dataset 1/3 arc-second. This dataset has 1/3 arc-second resolution, which equates to approximately 10-meter cell size raster data. Because this dataset was available as 1-degree ArcGrid raster blocks, a total of 4 individual, 1-degree blocks were merged together. This dataset was used to fill in land areas not covered by the 1/9 arc-second data or by other datasets described in this section. Further analysis indicated that near-shore values were not as accurate as other datasets; therefore, all data less than 2 meters (NAVD88), including all data in the ocean, were removed prior to merging the dataset.
  5. U.S. Coastal Relief Model – Southern California, 3 arc-second resolution. This dataset was available only in 3 arc-second resolution, which equates to approximately 90-meter cell size raster data. This dataset was available as an IMAGE raster for southern California (volume 6, version 1). This downloaded dataset was resampled to modify any internal depressions, ensuring that all cells drain out of the study area for hydrologic modeling purposes. This modified dataset then was used to complete the ocean part of the merged DEM that did not use data from the other four datasets.

More information for each of the datasets, publicly available, is described here.

 

Raster dataset

  • Download raster dataset in compressed zip format (coming soon)

 

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Project Chief: Wes Danskin
Phone: 619-225-6132
Email: wdanskin@usgs.gov


Welcome to the United States Geological Survey (USGS) San Diego Hydrogeology (SDH) project website, which provides geologic and hydrologic information for the transboundary San Diego–Tijuana area, USA and Mexico. This website provides background information about the project; a variety of news items; a large amount of data, in particular for USGS multiple-depth, monitoring-well sites; geologic and hydrologic models; and additional resources including photos, illustrations, and references.

Last updated: July 2023.

Some additional data may be available from the USGS database National Water Information System (NWIS).


Questions about San Diego Hydrogeology? Please contact Wes Danskin (email: wdanskin@usgs.gov or send a letter). 619.225.6132