Digital surface model (DSM) and digital elevation model (DEM) of the Los Padres Reservoir delta, Carmel River valley, CA, 2017-11-01

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Frequently anticipated questions:

What does this data set describe?

Title:
Digital surface model (DSM) and digital elevation model (DEM) of the Los Padres Reservoir delta, Carmel River valley, CA, 2017-11-01
Abstract:
This portion of the data release presents a digital surface model (DSM) and digital elevation model (DEM) of the exposed Los Padres Reservoir delta where the Carmel River enters the reservoir. The DSM and DEM have a resolution of 10 centimeters per pixel and were derived from structure-from-motion (SfM) processing of aerial imagery collected with an unoccupied aerial system (UAS) on 2017-11-01. The DSM represents the elevation of the highest object within the bounds of a cell, including vegetation, woody debris and other objects. The DEM represent the elevation of the ground surface where it was visible to the acquisiton system. Due to the nature of SfM processing, the DEM may not represent a true bare-earth surface in areas of thick vegetation cover; in these areas some DEM elevations may instead represent thick vegetation canopy. The raw imagery used to create these elevation models was acquired with a UAS fitted with a Ricoh GR II digital camera featuring a global shutter. The UAS was flown on pre-programmed autonomous flight lines spaced to provide approximately 70 percent overlap between images from adjacent lines. The camera was triggered at 1 Hz using a built-in intervalometer. The UAS was flown at an approximate altitude of 100 meters above ground level (AGL), resulting in a nominal ground-sample-distance (GSD) of 2.6 centimeters per pixel. The raw imagery was geotagged using positions from the UAS onboard single-frequency autonomous GPS. Twenty temporary ground control points (GCPs) consisting of small square tarps with black-and-white cross patterns were distributed throughout the area to establish survey control. The GCP positions were measured using real-time kinematic (RTK) GPS, using corrections from a GPS base station located on a benchmark designated SFML, located approximately 1 kilometer from the study area. The DSM and DEM have been formatted as cloud optimized GeoTIFFs with internal overviews and masks to facilitate cloud-based queries and display.
Supplemental_Information:
Additional information about the field activity from which these data were derived is available online at:
https://cmgds.marine.usgs.gov/fan_info.php?fan=2017-635-FA
Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
  1. How might this data set be cited?
    Logan, Joshua B., and East, Amy E., 20230111, Digital surface model (DSM) and digital elevation model (DEM) of the Los Padres Reservoir delta, Carmel River valley, CA, 2017-11-01: data release DOI:10.5066/P9J9CHOH, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

    This is part of the following larger work.

    Logan, Joshua B., and East, Amy E., 2023, Aerial imagery and structure-from-motion data products from a UAS survey of the Los Padres Reservoir delta, Carmel River valley, CA, 2017-11-01: data release DOI:10.5066/P9J9CHOH, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, CA.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -121.66731
    East_Bounding_Coordinate: -121.66118
    North_Bounding_Coordinate: 36.38117
    South_Bounding_Coordinate: 36.37326
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/63780c9ad34ed907bf70044b?name=LosPadresReservoir_2017-11-01_DSM_10cm_browse.jpg&allow=openTrue (JPEG)
    Color-shaded relief DEM of the Los Padres Reservoir delta.
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 01-Nov-2017
    Currentness_Reference:
    ground condition at time data were collected
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: GeoTIFF
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a Raster data set. It contains the following raster data types:
      • Dimensions, type Grid Cell
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 10
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -123.0
      Latitude_of_Projection_Origin: 0.0
      False_Easting: 500000.0
      False_Northing: 0.0
      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 0.100
      Ordinates (y-coordinates) are specified to the nearest 0.100
      Planar coordinates are specified in meters
      The horizontal datum used is NAD83 (National Spatial Reference System 2011) (EPSG:1116).
      The ellipsoid used is GRS 1980 (EPSG:7019).
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257222101.
      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name:
      North American Vertical Datum of 1988 (EPSG:5703), derived using GEOID03
      Altitude_Resolution: 0.001
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method:
      Explicit elevation coordinate included with horizontal coordinates
  7. How does the data set describe geographic features?
    GeoTIFF
    GeoTIFF containing elevation values. (Source: Producer defined)

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Joshua B. Logan
    • Amy E. East
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    Attn: PCMSC Science Data Coordinator
    2885 Mission Street
    Santa Cruz, CA

    831-427-4747 (voice)
    pcmsc_data@usgs.gov

Why was the data set created?

These data are intended to be used to characterize the position, elevation, volume, and morphology of the Los Padres Reservoir delta sediment where the Carmel River enters the reservoir. This assessment of reservoir sediment was made in response to the 2016 Soberanes Fire in the upper Carmel watershed, followed by high flows during water year 2017.

How was the data set created?

  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
    Date: 01-Nov-2017 (process 1 of 5)
    Aerial imagery was collected using a Department of Interior-owned 3DR Solo quadcopter fitted with a Ricoh GR II digital camera featuring a global shutter. The camera was mounted using a fixed mount on the bottom of the UAS and oriented in an approximately nadir orientation. During image acquisition the UAS was flown on pre-programmed autonomous flight lines at an approximate altitude of 100 meters above ground level (AGL), resulting in a nominal ground-sample-distance (GSD) of 2.6 centimeters per pixel. The flight lines were spaced to provide approximately 70 percent overlap between images from adjacent lines. The camera was triggered at 1 Hz using a built-in intervalometer and was programmed to acquire imagery in JPG format. Before each flight, the camera digital ISO, aperture and shutter speed were manually set to adjust for ambient light conditions. Although these settings were changed between flights, they were not permitted to change during a flight; thus, the images from each flight were acquired with consistent camera settings. Person who carried out this activity:
    Joshua Logan
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    Physical Scientist
    2885 Mission Street
    Santa Cruz, CA
    US

    831-460-7519 (voice)
    831-427-4748 (FAX)
    jlogan@usgs.gov
    Date: 01-Nov-2017 (process 2 of 5)
    Ground control was established using ground control points (GCPs) consisting of small square tarps with black-and-white cross patterns placed on the ground surface throughout the survey area. The GCP positions were measured using survey-grade GPS receivers operating in real-time kinematic (RTK) mode. For each GCP measurement the GPS receiver was placed on a fixed-height tripod and set to occupy each GCP for a minimum occupation time of one minute. The RTK corrections were referenced to a GPS base station occupying a previously established benchmark designated SFML, located on the Los Padres Reservoir dam approximately 1 kilometer from the survey area. In order to ensure consistency with historic surveys, the previously established position for SFML published in Smith and others, 2009 was used for the real-time surveys. After the survey, the static occupation on SFML was submitted to the National Geodetic Survey (NGS) Online Positioning User Service (OPUS). Person who carried out this activity:
    Joshua Logan
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    2885 Mission Street
    Santa Cruz, CA

    831-460-7519 (voice)
    jlogan@usgs.gov
    Date: 2022 (process 3 of 5)
    The image files were renamed using a custom python script. The file names were formed using the following pattern Fx-YYYYMMDDThhmmssZ_Ryz.*, where: - Fx = Flight number - YYYYMMDDThhmmssZ = date and time in the ISO 8601 standard, where 'T' separates the date from the time, and 'Z' denotes UTC ('Zulu') time. - Ry = RA or RB to distinguish camera 'RicohA' from 'RicohB' - z = original image name assigned by camera during acquisition - * = file extension (JPG or DNG)
    The approximate image acquisition coordinates were added to the image metadata (EXIF) ('geotagged') using the image timestamp and the telemetry logs from the UAS onboard single-frequency 1-Hz autonomous GPS. The geotagging process was done using the Geosetter software package. To improve timestamp accuracy, the image acquisition times were adjusted to true ('corrected') UTC time by comparing the image timestamps with several images taken of a smartphone app ('Emerald Time') showing accurate time from Network Time Protocol (NTP) servers. For this survey, +00:00:01 (1 second) was added to the image timestamp to synchronize with corrected UTC time. The positions stored in the EXIF are in geographic coordinates referenced to the WGS84(G1150) coordinate reference system (EPSG:4979), with elevation in meters relative to the WGS84 ellipsoid. Additional information was added to the EXIF using the command-line 'exiftool' software with the following command: exiftool ^ -P ^ -IPTC:Credit="U.S. Geological Survey" ^ -IPTC:Contact="pcmsc_data@usgs.gov" ^ -EXIF:Copyright="Public Domain" ^ -XMP:UsageTerms="Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty." ^ -EXIF:ImageDescription="Low-altitude aerial image of the Los Padres Reservoir delta area, Carmel River valley, California, USA, from USGS field activity 2017-635-FA; https://cmgds.marine.usgs.gov/fan_info.php?fan=2017-635-FA" ^ -XMP:Event="Unoccupied Aircraft System survey of Los Padres Reservoir delta area during USGS field activity 2017-635-FA." ^ -EXIF:GPSAreaInformation="Position from UAS onboard autonomous single-frequency GNSS." ^ -EXIF:GPSMapDatum="EPSG:4979 (WGS 84)" ^ -EXIF:Artist="U.S. Geological Survey, Pacific Coastal and Marine Science Center" ^ -IPTC:CopyrightNotice="Public Domain. Please credit U.S. Geological Survey." ^ -IPTC:Caption-Abstract="Aerial image of the Los Padres Reservoir delta area and Carmel River, Carmel River valley, California, USA, from an Unoccupied Aircraft System (UAS) during USGS field activity 2017-635-FA." ^ -sep ", " ^ -keywords="Carmel River, Los Padres Reservoir, Monterey County, California, 2017-635-FA, Unoccupied Aircraft System, UAS, drone, aerial imagery, U.S. Geological Survey, USGS, Pacific Coastal and Marine Science Center" ^ -comment="Aerial image of the Los Padres Reservoir delta area and Carmel River, Carmel River valley, California, USA, from an Unoccupied Aircraft System (UAS) during USGS field activity 2017-635-FA."^ -Orientation= ^ -XMP:AttributionURL="https://doi.org/10.5066/P9J9CHOH" ^ -OffsetTime*=+00:00 -AllDates+=7 ^ -r f* ^ -ext DNG ^ -ext JPG
    Additional metadata tags were populated in the imagery metadata using the following command: exiftool ^ -P ^ "-XMP-photoshop:Credit<IPTC:Credit" ^ "-XMP-iptcCore:CreatorWorkEmail<IPTC:Contact" ^ "-XMP-dc:Rights<EXIF:Copyright" ^ "-XMP-dc:Description<EXIF:ImageDescription" ^ "-XMP-exif:all<GPS:all" ^ "-XMP-exif:GPSLatitude<Composite:GPSLatitude" ^ "-XMP-exif:GPSLongitude<Composite:GPSLongitude" ^ "-XMP-exif:GPSDateTime<Composite:GPSDateTime" ^ "-XMP-photoshop:DateCreated<EXIF:DateTimeOriginal" ^ "-XMP-xmp:ModifyDate<EXIF:ModifyDate" ^ "-XMP-dc:Creator<EXIF:Artist" ^ "-XMP-tiff:Make<EXIF:Make" ^ "-XMP-tiff:Model<EXIF:Model" ^ -overwrite_original ^ -ext JPG Person who carried out this activity:
    Joshua Logan
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    2885 Mission Street
    Santa Cruz, CA

    831-460-7519 (voice)
    jlogan@usgs.gov
    Date: 2018 (process 4 of 5)
    Structure-from-motion (SfM) processing techniques were used to create point clouds, DSMs, and orthomosaic images in the Agisoft Photoscan/Metashape software package using the following workflow: 1. Initial image alignment was performed with the following parameters - Accuracy: 'high'; Pair selection: 'reference', 'generic'; Key point limit: 0 (unlimited); Tie point limit: 0 (unlimited). 2. Sparse point cloud error reduction was performed using an iterative gradual selection and camera optimization process with the following parameters: Reconstruction Uncertainty: 10; Projection Accuracy: 3. Lens calibration parameters f, cx, cy, k1, k2, k3, p1, and p2 were included in the optimization. Additional sparse points obviously above or below the true surface were manually deleted after the last error reduction iteration. 3. Ground control points (GCPs) were automatically detected using the 'Cross (non-coded)' option. False matches were manually removed, and all markers were visually checked and manually placed or adjusted if needed. 4. Additional sparse point cloud error reduction was performed using an iterative gradual selection and camera optimization process with the following parameters: Reprojection Error: 0.3. Lens calibration parameters f, cx, cy, k1, k2, k3, p1, and p2 were initially included in the optimization, but additional parameters k4, b1, b2, p3, and p4 were included once Reprojection Error was reduced below 1 pixel. Additional sparse points obviously above or below the true surface were manually deleted after the last error reduction iteration, and a final optimization was performed. 5. A dense point cloud was created using the 'high' accuracy setting, with 'aggressive' depth filtering. 6. A preliminary Digital Surface Model (DSM) with a native resolution of 4.8 centimeters per pixel was created using all points in the dense point cloud. 7. An RGB orthomosaic with a native resolution of 2.4 centimeters per pixel was created using the preliminary DSM as the orthorectification surface, and then exported to a GeoTIFF format with a 2.5-centimeter pixel resolution. 8. The dense point cloud was classified using the Agisoft Photoscan "Classify Ground Points" tool with the following settings: Max. angle: 30 degrees Max. distance: 0.5 m Cell size: 20 m 9. The classified dense point cloud was exported to an LAZ format, with LAS classes 0 (unclassified), 2 (ground), and 7 (noise). 10. The orthomosaic was used as a background map to digitize a polygon of the water surface of the reservoir. 11. The LAStools lasclip utility was used to classify all points within the water surface polygon as class 9, "water". 12. The DEM raster file was created using the LAStools lasgrid utility to calculate the average elevation of points classified as class 2, "ground" (ignoring all other point classes) within each 10 cm raster cell. No hole filling was performed. 13. The DSM raster file was created using the LAStools lasgrid utility to calculate the highest elevation of all points (ignoring class 7, "noise") within each 10 cm raster cell. No hole filling was performed. Person who carried out this activity:
    Joshua Logan
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    Physical Scientist
    2885 Mission Street
    Santa Cruz, CA
    US

    831-460-7519 (voice)
    831-427-4748 (FAX)
    jlogan@usgs.gov
    Date: 2022 (process 5 of 5)
    A uniform spatial adjustment was applied to the rasters to shift the data from the historic reference frame published in Smith and others, 2009 to the updated reference frame observed at the SFML benchmark during the 2017 survey (derived using the National Geodetic Survey (NGS) Online Positioning User Service (OPUS)).
    To ensure consistency with historic data sets, the original published position for the SFML benchmark was used for the RTK GPS base station position. Thus, the GCP positions and original SfM data products were consistent with the historic data presented in Smith and others, 2009. The SFML benchmark position published in that report is (in UTM zone 10 coordinates relative to the NAD83 reference frame): Northing: 4027605.397 Easting: 619388.986 Ortho. Ht. [m, NAVD88]: 322.418 (GEOID03)
    After the 2017-11-01 UAS survey, the 5:40 static GPS occupation on SFML was submitted to NGS OPS which derived the following current-epoch position for SFML: Northing: 4027605.687 Easting: 619388.761 Ortho. Ht. [m, NAVD88]: 322.359 (using GEOID03 separation = -33.047 m)
    Thus, the displacement between the 2009 published SFML position and the 2017-11-01 observed position is: dN: +0.290 meters dE: -0.225 meters dElev.: -0.059 meters
    This magnitude and direction of displacement is similar to those estimated for this location by the National Geodetic Survey Horizontal Time-Dependent Positioning (HTDP), shown below: HTDP OUTPUT, VERSION 3.4.0 DISPLACEMENTS IN METERS RELATIVE TO NAD_83(2011/CORS96/2007) FROM 11-05-2008 TO 11-01-2017 (month-day-year) FROM 2008.847 TO 2017.835 (decimal years) NAME OF SITE: SFML LATITUDE: 36 23 10.23945 N LONGITUDE: 121 40 7.85831 W NORTH: 0.341 meters EAST: -0.241 meters UP: -0.012 meters
    To produce the final data products for this data release, all data were transformed from the historic reference frame into the current-epoch reference frame consistent with the 2017-11-01 observed position for SFML. This transformation was done using a uniform horizontal and vertical adjustment.
    For adjustment of the DSM and DEM, the following adjustment process was used: 1. Each raster was shifted horizontally using the gdal_translate utility: gdal_translate ^ -a_ullr 619540.975 4027043.690 620036.075 4026189.290 ^ original.tif ^ hz_shifted.tif 2. The gdalwarp utility was used to re-interpolate the raster values at the original cell boundaries using bilinear interpolation (to maintain cell alignement with other data products in this data release): gdalwarp ^ -r bilinear ^ -tr 0.10 0.10 ^ -te 619541.200 4026189.000 620036.300 4027043.400 ^ -srcnodata -3.402823e+38 ^ hz_shifted.tif ^ hz_shifted_aligned.tif 3. The gdal_calc utility was used to apply the vertical adjustment to the elevation values in each raster: gdal_calc ^ -A hz_shifted_aligned.tif ^ --outfile=hz_shifted_aligned_vertadjusted.tif ^ --NoDataValue=-3.402823e+38 ^ --calc="A - 0.059" 4. The adjusted raster was converted to a cloud optimized GeoTIFF for the final data product using gdal_translate: gdal_translate ^ -of COG -a_srs EPSG:6339 -stats -co BLOCKSIZE=256 -co COMPRESS=DEFLATE -co PREDICTOR=3 ^ -co NUM_THREADS=ALL_CPUS --config GDAL_CACHEMAX "50%" ^ --config GDAL_MAX_DATASET_POOL_SIZE 512 ^ hz_shifted_aligned_vertadjusted.tif ^ hz_shifted_aligned_vertadjusted_COG.tif Person who carried out this activity:
    Joshua Logan
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    2885 Mission Street
    Santa Cruz, CA

    831-460-7519 (voice)
    jlogan@usgs.gov
  3. What similar or related data should the user be aware of?
    Smith, D.P., Kvitek, R., Aiello, I., Iampietro, P., Quan, C., Paddock, E., Endris, C., and Gomez, K., 2009, Fall 2008 Stage-Volume Relationship for Los Padres Reservoir, Carmel Valley, California: Prepared for the Monterey Peninsula Water Management District.

    Online Links:

    Other_Citation_Details:
    Smith, D.P., Kvitek, R., Aiello, I., Iampietro, P., Quan, C., Paddock, E., Endris, C, and Gomez, K., 2009, Fall 2008 Stage-Volume Relationship for Los Padres Reservoir, Carmel Valley, California: Prepared for the Monterey Peninsula Water Management District. The Watershed Institute, California State University Monterey Bay, Publication no. WI-2009-2, 30 pp.

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?
    No formal attribute accuracy tests were conducted.
  2. How accurate are the geographic locations?
    Horizontal accuracy was estimated by comparing ground control point (GCP) positions measured with RTK GPS measurements to their SfM-estimated positions. Due to the time-intensive process of placing GCPs in the field, all available GCPs were used for registration and camera optimization in the SfM processing workflow during the creation of the final SfM data products. To evaluate the horizontal positional accuracy of the final SfM alignments, each GCPs was disabled one-at-a-time using a python script to create a 'temporary check point'. With a single GCP temporarily disabled, camera optimization was performed with all lens parameters fixed, and all other GCPs enabled. The residual errors of the check point relative to its GPS-measured position were recorded. After all temporary check point iterations were complete, the root-mean-square error (RMSE) and mean-absolute error (MAE) were calculated. The resulting horizontal RMSE was 0.025 meters (MAE 0.020 meters). The addition of the estimated horizontal GPS uncertainty (0.020 meters) in quadrature results in a total horizontal accuracy estimate of 0.032 meters. It should be noted that this error estimate is for areas of bare ground or low vegetation where GCPs were placed. Additional sources of error such as poor image-to-image point matching due to vegetation or uniform substrate texture (such as sand) resulting in poor surface reconstruction may cause localized errors in some portions of the point clouds to exceed this estimate.
  3. How accurate are the heights or depths?
    Vertical accuracy was estimated using two methods to compare the DSM and DEM vertical elevations to concurrently collected real-time kinematic (RTK) GPS measurements. The first method used a comparison of ground control point (GCP) positions measured with RTK GPS measurements to their SfM-estimated positions. Due to the time-intensive process of placing GCPs in the field, all available GCPs were used for registration and camera optimization in the SfM processing workflow during the creation of the final DSM and DEM. To evaluate the vertical positional accuracy of the models after processing was completed, a subset of GCPs was disabled one-at-a-time using a python script to create 'temporary check points'. With a single GCP temporarily disabled, camera optimization was performed with all lens parameters fixed, and all other GCPs enabled. The residual errors of the check point relative to its GPS-measured position were recorded. After all temporary check point iterations were complete, the root-mean-square error (RMSE) and mean-absolute error (MAE) were calculated. The resulting vertical RMSE was 0.039 meters (MAE 0.028 meters). The addition of the estimated vertical GPS uncertainty (0.040 meters) in quadrature results in a total vertical accuracy estimate of 0.056 meters for the point cloud. It should be noted that this error estimate is for areas of bare ground or low vegetation where GCPs were placed. Additional sources of error such as poor image-to-image point matching due to vegetation or uniform substrate texture (such as sand) resulting in poor surface reconstruction may cause localized errors in some portions of the point clouds to exceed this estimate. A second method was used to attempt to quantify the vertical errors in areas away from the GCPs. During field data collection, topographic measurements on unvegetated areas were collected with backpack-mounted RTK GPS. These measurements were compared to the elevation models using bilinear interpolation at each GPS point to derive additional accuracy estimates. - For the DSM, the vertical RMSE of 821 backpack-mounted RTK GPS measurements compared to the DSM elevations at those locations was 0.059 meters (MAE 0.047 meters). The mean-error (vertical bias) of the GPS measurements relative to DSM elevations was 0.017 meters, meaning the DSM was, on average, lower than the GPS measurements. The addition of the estimated vertical uncertainty of the backpack-mounted GPS (0.050 meters) in quadrature results in a total vertical accuracy estimate of 0.077 meters for the DSM using this method. - For the DEM, the vertical RMSE of 821 backpack-mounted RTK GPS measurements compared to the DEM elevations at those locations was 0.060 meters (MAE 0.049 meters). The mean-error (vertical bias) of the GPS measurements relative to DSM elevations was 0.024 meters, meaning the DEM was, on average, lower than the GPS measurements. The addition of the estimated vertical uncertainty of the backpack-mounted GPS (0.050 meters) in quadrature results in a total vertical accuracy estimate of 0.078 meters for the DEM using this method. These slightly higher error estimates are due in part to the less precise nature of the backpack-mounted GPS measurements. However, these backpack-mounted GPS comparisons do provide a more conservative, spatially distributed estimate of the true accuracy of the elevations models than the GCP check point method. We present both estimates here to provide the end-user with a more complete understanding of the accuracy of the final data products.
  4. Where are the gaps in the data? What is missing?
    Dataset is considered complete for the information presented, as described in the abstract. For the purpose of creating the DSM and the DEM, the small exposed 3 x 4 meter island located in the reservoir approximately 10 meters north of the delta was omitted. Users are advised to read the rest of the metadata record carefully for additional details.
  5. How consistent are the relationships among the observations, including topology?
    No formal logical accuracy tests were conducted.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints None
Use_Constraints USGS-authored or produced data and information are in the public domain from the U.S. Government and are freely redistributable with proper metadata and source attribution. Please recognize and acknowledge the U.S. Geological Survey as the originator(s) of the dataset and in products derived from these data. This information is not intended for navigation purposes.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey - ScienceBase
    Denver Federal Center, Building 810, Mail Stop 302
    Denver, CO
    United States

    1-888-275-8747 (voice)
    sciencebase@usgs.gov
  2. What's the catalog number I need to order this data set? The Los Padres Reservoir DSM and DEM (LosPadresReservoir_2017-11-01_DSM_10cm.tif, and LosPadresReservoir_2017-11-01_DEM_10cm.tif) are available as Cloud Optimized GeoTIFF files.
  3. What legal disclaimers am I supposed to read?
    Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data on any other system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty.
  4. How can I download or order the data?
  5. What hardware or software do I need in order to use the data set?
    These data can be viewed with GIS software or other software capable of displaying geospatial raster data.

Who wrote the metadata?

Dates:
Last modified: 11-Jan-2023
Metadata author:
U.S. Geological Survey, Pacific Coastal and Marine Science Center
Attn: PCMSC Science Data Coordinator
2885 Mission Street
Santa Cruz, CA

831-427-4747 (voice)
pcmsc_data@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/pcmsc/DataReleases/ScienceBase/DR_P9J9CHOH/LosPadresReservoir_2017-11-01_DSM_DEM_metadata.faq.html>
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