OC Survey – Geospatial Data Products:
OC Survey is distributing various Geospatial data sets that have been produced and distributed by the United
States Geological Survey (USGS) as well as a few products created by the OC Survey Geospatial/Geodetic
unit. These data sets are used to support the USGS National Elevation Dataset (NED) and FEMA Floodplain
mapping. These data sets and products can be valuable resources for various planning and analysis activities
such as hydrological, slope, elevation, etc. OC Survey provides no warranty, expressed or implied, as to the
accuracy, reliability, or completeness of the furnished data.
We are currently providing two USGS data sets being:
1) LiDAR - . Millions of 3-dimensional data points
(LAS file)
2) DEM - Digital elevation model
(TIF file)
We are currently providing three OC Survey data products being:
1) CONTOURS – Estimated elevations at either 2 foot
or 20 foot intervals
(SHP & KMZ file)
2) PARCELS – Parcel lines
(SHP & KMZ file)
3) HILLSHADE DEM – Hill shade relief
(TIF & KMZ file)
4) COLORED HILLSHADE DEM – Hill shade relief
(TIF & KMZ file)
All Geospatial data products are based on the same data set. The contours were generated from the DEM.
The DEM was generated from the LiDAR data. With this, one needs to understand the specifics of the LiDAR
data in order to properly use these products.
LiDAR Meta Data (per USGS):
Time period of collection: December 17, 2011 to February 9, 2012
Nominal Pulse Spacing (NPS): 1 meter (estimated average of irregular point spacing)
Coverage of 682 square miles of Orange County which excludes the eastern portion of the County as defined
in the Google Earth KMZ file.
Vertical Accuracies (95%):
Fundamental Vertical Accuracy (FVA) open non-vegetated terrain =
Supplemental Level Accuracy (SLA) individual land cover categories =
300 N. Flower Street, Santa Ana, CA 92703
P.O. Box 4048, Santa Ana, CA 92702-4048
0.25 meters (0.8 feet)
0.36 meters (1.2 feet)
www.ocpublicworks.com
Revised 2016.02.09
Consolidated Accuracy (CLA) combined land cover categories =
0.36 meters (1.2 feet)
Raw and classified point cloud fully compliant LAS version with option of v1.2 or 1.3 and Point Record Format
1,3,4, or 5
Hydro-flattened
Reference System:
To use the data set and products properly, one must understand the reference frames they are based upon. All
data is on the same datum being North American Datum 1983 (NAD83), 2007.00 Epoch. The projections and
units are as follows:
LiDAR -
Horizontal = UTM Zone 11 N, NAD83 (Meters)
Vertical = NAVD 88 (Meters)
DEM -
Horizontal = CCS83, Zone VI, (US Feet)
Vertical = NAVD 88 (US Feet)
PARCEL LINES -
Horizontal = CCS83, Zone VI, (US Feet)
CONTOURS -
Horizontal = CCS83, Zone VI, (US Feet)
Vertical = NAVD 88 (US Feet)
HILLSHADE DEM -
Horizontal = CCS83, Zone VI, (US Feet)
Vertical = NAVD 88 (US Feet)
COLORED HILLSHADE DEM -
Horizontal = CCS83, Zone VI, (US Feet)
Vertical = NAVD 88 (US Feet)
Google Earth KMZ
We have created a Google Earth (GE) KMZ file which contains a County wide grid based on the USGS LiDAR
grid (1500m x 1500m). Selecting any of the grids will give you the option to download any data product
available within that grid. All files are in a zipped file format except for the KMZ files.
The KMZ files will immediately open in GE. All other files must be downloaded and saved on your PC.
Note: these files are large, specially the LiDAR files. Be patient when downloading.
When downloading, you may receive an error such as;
300 N. Flower Street, Santa Ana, CA 92703
P.O. Box 4048, Santa Ana, CA 92702-4048
www.ocpublicworks.com
Revised 2016.02.09
Or
Ignore these. You should shortly receive a File Download window such as;
All files EXCEPT the LiDAR .LAS files can be viewed in GE simply by “import” or “drag and drop” into GE.
You will also find within the kmz file, a polygon labeled “1 meter DEM extent”. This polygon defines the most
current and highest resolution data (1 meter) that USGS offers. Data outside this area is a lower resolution (10
meter resampled to 1 meter) and can be quite outdated and must be used with caution.
Within the “1 meter DEM extent”, you will find;
LiDAR .LAS files
1 meter DEM .TIFF files
2 Foot Contours .SHP files
300 N. Flower Street, Santa Ana, CA 92703
P.O. Box 4048, Santa Ana, CA 92702-4048
(2011 - 1 meter NPS)
(2011 - 1 meter high resolution)
(based on above DEM)
www.ocpublicworks.com
Revised 2016.02.09
Outside of the “1 meter DEM extent”, you will find;
1 meter DEM .TIFF files
20 Foot Contours .SHP files
(older and 10 meter lower resolution resampled to 1 meter)
(based on above DEM)
Please contact myself for any questions that arise,
Art Andrew
OC Survey - Geospatial & Geodetic Unit
[email protected]
714.967.0823
Google Earth Helpful Hints:
1. “I can’t see the parcel layer” – if you’ve opened the parcel kmz and the Hillshade kmz, the parcel
lines are below the hillshade. To bring them to the top, you must right click on the hillshade.tif file (not
the folder) and select Properties.
Then select Altitude and change “Clamped to ground” to “Clamped to sea floor”.
2. “How do I control the Hillshade Transparency?” - right click on the hillshade.tif file (not the folder)
and select Properties. You will see a Transparency bar. Sliding this bar between Clear and Opaque
controls the transparency.
300 N. Flower Street, Santa Ana, CA 92703
P.O. Box 4048, Santa Ana, CA 92702-4048
www.ocpublicworks.com
Revised 2016.02.09