2016 Orthophotography and Lidar

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Updates

2016

March 11 - Flying begins for both Lidar and imagery
April 18 - Imagery and Lidar collection completed
March 7 – Tile delivery grid finalized
May - Pilot imagery tiles received by CRCOG
June  -  QA/QC Firm selected to do independent review
June – Pilot lidar tiles received by CRCOG
November – Decision made to get two types of MrSID (generation 3 and generation 4) to meet needs or all users
December  - Imagery tiles for blocks 1, 3, 5, 7 (western half of the state) approved by QA/QC process
December 29 – UConn receives Blocks 1, 3, 5, 7 imagery tiles and begins processing

2017

January – Imagery tiles for blocks 2, 4 (eastern half, south and central) approved by QA/QC process 
January 24 – Imagery tiles for blocks 2, 4 (eastern half, south and central) received by UConn
February 10 - all imagery approved by QA/QC process
February 13 - Imagery tiles for block 6, the last one, (northeast) received by UConn

Note that the QA/QC process is very important and has been thorough.  It has delayed the original timeline a bit.

 

The Facts

23,381 tiles covering Connecticut. Each tile is 2500ft on a side or 0.224 sq miles, 143.5 acres and 6,250,000 sq feet.

The Facts: Imagery

Statewide. 4 bands (red, green, blue, near-infrared).  3 inch pixels.  GeoTIFFs.  MrSIDs Generation 3 and Generation 4. CT State Plane NAD 83 Feet. XX TB of GeoTIFFs and XX GB of MrSIDs (Generation 3 is xx and Generation xx is ). Captured in March and April 2016 (leaf off).  Tide coordinated.  

The Facts: Elevation

Statewide. USGS Quality Level 2. 2 points per sq meter. Ground/non-ground classification. LAS files (point cloud). Bare earth 1m pixel raster tiles (called a Digital Elevation Model or DEM). 1 foot and 5 foot contours derived from Lidar. Intensity images. Captured in March and April 2016 (leaf off).  Tide coordinated.

 

Image Formats

GeoTIFF Highest quality image available here but also the largest file size by a lot.
MrSID Generation 4 Compressed image file that supports all 4 image bands (blue, green, red, near-infrared)
MrSID Generation 3 Compressed image file with the smallest file size because it contains only 3 image bands (blue, green, red)

 

TIFF or TIF stand for Tagged Image File Format and is used for storing raster images of all kinds. Geo indicates that the TIF has a word file, called TWF that stores geographic information about the raster file.

MrSID stands for MultiresolutionSeamless Image Database. It is a way of compressing imagery so that it can be quickly viewed. LizardTech pioneered the MrSID technology. With each Generation, LizardTech has improved the functions of the MrSID files. MrSID Generation 3 improved upon Generation 2 by supporting unlimited files sizes, lossless encoding with optimization and manipulation options. MrSID Generation 4 improved upon Generation 3 by supporting multi-spectral and hyper-spectral imagery and an improved mechanism for composite mosaicking. Read the full explanation on the LizardTech website.

Tiles and Sizes

Block Number of Tiles File size: GeoTIFF File Size: MrSID Gen 3 File Size: MrSID Gen 4 File Size: DEM
1 3881 1.41 TB 54.2 GB 72.4 GB  
2 4169 1.51 TB 58.2 GB 77.7 GB  
3 3239 1.15 TB 45.2 GB 60.4 GB  
4 3200 1.16 TB 44.7 GB 59.6 GB  
5 3061 1.11 TB 42.8 GB 57.0 GB  
6 3617 1.31 TB 50.5 GB 67.4 GB  
7 2214 825 GB 30.9 GB 41.2 GB  
TOTAL 23,381 8.475 TB 326.5 GB 435.7 GB  
Mosaic