2016 Orthophotography and Lidar

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Updates | Metadata | The Facts | Image Formats | Tile Grid | Tiles & Sizes | Metadata | Coordinate Systems

 

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
February 22 - dynamic map service and tiled map service completed for the state. All tiles available for download.
March 27 - town mosaics arrive at CLEAR
April 3 - town mosaics available for download
May 22 - lidar DEM metadata and DEM tiles for blocks 3, 5, 7 arrive at CLEAR
May 23 - lidar DEM tiles for blocks 3, 5 and 7 available for download

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 (2011)* Feet. 8.5 TB of GeoTIFFs and 763 GB of MrSIDs (Generation 3 is 327 GB and Generation 4 is 436 GB). 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.

* NAD 83 (2011) is the most current realization of NAD 83 published by the National Geodetic Survey and is consistent with the national Continuously Operating Reference Stations (CORS) Network.

 

Metadata

FGDC Metadata is available for the 2016 aerial imagery and the 2016 lidar DEM.

2016 Aerial Imagery Metadata Correction

The current version contains several corrections. The imagery tiles available for download contain the older version of the metadata file. Please note these corrections.

A correction was made in the Description, Purpose section. The correct information is:

Purpose: Rectified orthoimagery is for public use.

A correction was made in the Data Access Constraints section. The correct information is:

Access constraints: None. This data is in the public domain.
Use constraints: None. Users can copy, modify, distribute and perform work, even for commercial purposes, without requesting permission.

A correction as in the Metadata, Metadata Access Contraints section. The correct information is:

Access constraints: None. This data is in the public domain.
Use constraints:
None. Users can copy, modify, distribute and perform work, even for commercial purposes, all without requesting permission.

To download the corrected xml, click here to open it in a web browser. Browsers are all different, but find the place where you can save the page and save the ortho_2016.xml file to your computer.

 

Delivery Area and Tile Grid

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  
Town
Mosaics
169 towns - 631 GB 869 GB