This is a mosaic of bare-earth digital elevation model (DEM) surfaces of the San Joaquin Valley from 2021. This mosaic only includes the section of the valley that corresponds to California State Plane Zone 3. Horizontal spatial reference is NAD 1983 (2011) California State Plane Zone 3. Vertical spatial reference is NAVD 1988 with Geoid 18. Raster resolution is 1 ft. All units are in US Survey Feet.

Technically these are not final deliverables, as they have not yet undergone USGS review, and are still being reviewed by DWR’s to validate they meet project requirements and project specifications. DWR’s aerial mapping consultant, Towill, Inc., has cleared this dataset to meet project requirements and project specifications under the direction of their California Licensed Land Surveyor.

The DEMs for this mosaic were created from raw lidar point clouds that were collected by aircraft between 2/21/2021 and 4/30/2021.

Towill conducted the aerial lidar acquisition and NV5 Geospatial processed the raw data.

Below is some summary information of the acquisition:

Aircraft: Aspen Partenavia P-68, Tail Numbers: 300LF, N68VA

Flight Altitude (AGL): 1600 m

Field of View: 40 degrees

Minimum Side Overlap: 30%

RMSEz: < 10 cm

Lidar Sensor: Optech Galaxy Prime - serial Number 5060411

Average Point Density: 10 pts / sq. meter

Below is a summary of the lidar processing process used:

Applanix + POSPac software was used for post-processing of airborne GPS and inertial data (IMU), which is critical to the positioning and orientation of the lidar sensor during all flights. Applanix POSPac combines aircraft raw trajectory data with stationary GPS base station data yielding a “Smoothed Best Estimate Trajectory” (SBET) necessary for additional post processing software to develop the resulting geo-referenced point cloud from the lidar missions.

During the sensor trajectory processing (combining GPS & IMU datasets) certain statistical graphs

and tables are generated within the Applanix POSPac processing environment which are commonly used as indicators of processing stability and accuracy. This data for analysis include: max horizontal / vertical GPS variance, separation plot, altitude plot, PDOP plot, base station baseline length, processing mode, number of satellite vehicles, and mission trajectory.

Point clouds were created using the Optech LMS software. The generated point cloud is the mathematical three dimensional composite of all returns from all laser pulses as determined from the aerial mission.

The point cloud is imported into GeoCue distributive processing software. Imported data is tiled and then calibrated using TerraMatch and proprietary software. Using TerraScan, the vertical accuracy of the surveyed ground control is tested and any bias is removed from the data. TerraScan and TerraModeler software packages are then used for automated data classification and manual cleanup. The data are manually reviewed and any remaining artifacts removed using functionality provided by TerraScan and TerraModeler.

DEMs and Intensity Images are then generated using proprietary software. In the bare earth surface model, above-ground features are excluded from the data set. Global Mapper is used as a final check of the bare earth dataset.

Finally, proprietary software is used to perform statistical analysis of the LAS files.

This is an official DWR Image Service, which meets all appropriate requirements of the DWR Spatial Data Standards, specifically the DWR Spatial Data Standards version 3.5, dated April 12, 2023.

DWR makes no warranties or guarantees — either expressed or implied — as to the completeness, accuracy, or correctness of the data. DWR neither accepts nor assumes liability arising from or for any incorrect, incomplete, or misleading subject data.

This Image Service was published on 4/12/2023 by the DWR Division of Engineering. Comments, problems, improvements, updates, or suggestions should be forwarded to gis@water.ca.gov as available and appropriate.

This is a mosaic of bare-earth digital elevation model (DEM) surfaces of the San Joaquin Valley from 2021. This mosaic only includes the section of the valley that corresponds to California State Plane Zone 3. Horizontal spatial reference is NAD 1983 (2011) California State Plane Zone 3. Vertical spatial reference is NAVD 1988 with Geoid 18. Raster resolution is 1 ft. All units are in US Survey Feet.

Technically these are not final deliverables, as they have not yet undergone USGS review, and are still being reviewed by DWR’s to validate they meet project requirements and project specifications. DWR’s aerial mapping consultant, Towill, Inc., has cleared this dataset to meet project requirements and project specifications under the direction of their California Licensed Land Surveyor.

The DEMs for this mosaic were created from raw lidar point clouds that were collected by aircraft between 2/21/2021 and 4/30/2021.

Towill conducted the aerial lidar acquisition and NV5 Geospatial processed the raw data.

Below is some summary information of the acquisition:

Aircraft: Aspen Partenavia P-68, Tail Numbers: 300LF, N68VA

Flight Altitude (AGL): 1600 m

Field of View: 40 degrees

Minimum Side Overlap: 30%

RMSEz: < 10 cm

Lidar Sensor: Optech Galaxy Prime - serial Number 5060411

Average Point Density: 10 pts / sq. meter

Below is a summary of the lidar processing process used:

Applanix + POSPac software was used for post-processing of airborne GPS and inertial data (IMU), which is critical to the positioning and orientation of the lidar sensor during all flights. Applanix POSPac combines aircraft raw trajectory data with stationary GPS base station data yielding a “Smoothed Best Estimate Trajectory” (SBET) necessary for additional post processing software to develop the resulting geo-referenced point cloud from the lidar missions.

During the sensor trajectory processing (combining GPS & IMU datasets) certain statistical graphs

and tables are generated within the Applanix POSPac processing environment which are commonly used as indicators of processing stability and accuracy. This data for analysis include: max horizontal / vertical GPS variance, separation plot, altitude plot, PDOP plot, base station baseline length, processing mode, number of satellite vehicles, and mission trajectory.

Point clouds were created using the Optech LMS software. The generated point cloud is the mathematical three dimensional composite of all returns from all laser pulses as determined from the aerial mission.

The point cloud is imported into GeoCue distributive processing software. Imported data is tiled and then calibrated using TerraMatch and proprietary software. Using TerraScan, the vertical accuracy of the surveyed ground control is tested and any bias is removed from the data. TerraScan and TerraModeler software packages are then used for automated data classification and manual cleanup. The data are manually reviewed and any remaining artifacts removed using functionality provided by TerraScan and TerraModeler.

DEMs and Intensity Images are then generated using proprietary software. In the bare earth surface model, above-ground features are excluded from the data set. Global Mapper is used as a final check of the bare earth dataset.

Finally, proprietary software is used to perform statistical analysis of the LAS files.

This is an official DWR Image Service, which meets all appropriate requirements of the DWR Spatial Data Standards, specifically the DWR Spatial Data Standards version 3.5, dated April 12, 2023.

DWR makes no warranties or guarantees — either expressed or implied — as to the completeness, accuracy, or correctness of the data. DWR neither accepts nor assumes liability arising from or for any incorrect, incomplete, or misleading subject data.

This Image Service was published on 4/12/2023 by the DWR Division of Engineering. Comments, problems, improvements, updates, or suggestions should be forwarded to gis@water.ca.gov as available and appropriate.