2011 FEMA Lidar: Modoc, California

Create custom data files by choosing data area, product type, map projection, file format, datum, etc. A new metadata will be produced to reflect your request using this record as a base. Change to an orthometric vertical datum is one of the many options.

Bulk download of data files in LAZ format, geographic coordinates, orthometric heights. Note that the vertical datum (hence elevations) of the files here are different than described in this document. They will be in an orthometric datum.

The Data Access Viewer (DAV) allows a user to search for and download elevation, imagery, and land cover data for the coastal U.S. and its territories. The data, hosted by the NOAA Office for Coastal Management, can be customized and requested for free download through a checkout interface. An email provides a link to the customized data, while the original data set is available through a link within the viewer.

This graphic displays the footprint for this lidar data set.

Link to data set report.

Link to data set report.

Digital Mapping Inc.

1-Acqusition:

Modoc LIDAR acquisition consisted of 26 flight lines with 2 cross flights. Alturas Airport was flown for the airport calibration. Two base stations were used for the project. The LIDAR misson was flown in 05/04/2011.

ALTM Gemini was used as the LIDAR scanner. LIDAR flight settings were:

Altitude (m): 1200

System PRF (kHz): 70

Scan Freq (Hz): 39

Scan Angle +/-: 17

Desired Res (m): 0.804

PPM^2: 1.55

2-Processing:

LIDAR data were processed and fit to the ground using DASHMap, GeoCue, TerraScan and TerraMatch softwares. All the data were calibrated to determine and eliminate systematic biases that might occur within the hardware of the ALTM Gemini system. A total of 11 aerial targets were surveyed and used to fit the LIDAR data to the ground. Ground point were removed from the top of bridges. LAS tiles that touch processing limit are classified however QA\QC of the ground points were done to the data which were within processing limit. LAS tiles are classified into 6 classes:

1 processed, but unclassified

2 bare-earth ground

7 noise

9 water

10 ignored

11 withheld

3-Breaklines:

Breaklines were compiled for streams, lakes, ponds and man-made features -bridges, culverts- that constrict or control the flow of water in 3D data collection mode from LIDAR data. Breaklines were not collected for the areas outside the processing limit.

Ponds and lakes are collected as polygons. They have constant elevation and they have elevation values less than the surrounding ground points.

For dry streams and streams narrower than 50 feet single stream breaklines were collected. For streams wider than 50 feet edges of the streams were collected along with stream centerline. The project area was relatively flat which made it some of the streams having single elevation across. Stream breaklines were broken at culverts and not broken at bridges.

Culvert breaklines snap to stream endpoints on both sides and have the same elevation as the stream breakline at the snapping location.

Top and bottom of the bridge breaklines were collected.

Breaklines are delivered as ESRI geodatabase file format. Topology rules were applied to the breaklines. Breaklines snap to each other, split at intersections, not self-intersect or overlap each other.

4-Low Confidence Areas:

Areas that may not meet the data accuracy requirements due to heavy vegetation were compiled as 2D polygon. Special effort was given to minimize these areas.

Ground points were tried to be classified from dense vegetation areas where possible using manual techniques.

NOAA Office for Coastal Management (OCM) received 92 lidar point cloud files in las format. The files contained lidar elevation and intensity measurements. The data were in California State Plane Zone 1 (NAD83), international feet coordinates and NAVD88 (Geoid03) elevations in international feet. The data were classified as: 1-Unclassified, 2-Ground, 7-Noise, 9-Water, 10-Ignored Ground & 11-Withheld. OCM processed all classifications of points to the Digital Coast Data Access Viewer (DAV).

OCM performed the following processing on the data for Digital Coast storage and provisioning purposes:

1. An internal OCM script was run to check the number of points by classification and by flight ID and the gps and intensity ranges.

2. Internal OCM scripts were run on the laz files to convert from orthometric (NAVD88) elevations to ellipsoid elevations using the Geoid 03 model, to convert to geographic coordinates, to convert from vertical units feet to meters, to assign the geokeys, to sort the data by gps time, and zip the data to database and to http.