MassGIS Data - LiDAR Terrain Data

2002-2012

Overview

Click to see the full size image.

These seventeen datasets contain Light Detection and Ranging (LiDAR) terrain files covering most of eastern Massachusetts, as well as portions of Hampden County. These data can be used for emergency response, drainage studies and hydrologic / floodplain modeling, development suitability analysis and infrastructure planning, identification of structures and other man-made features, habitat classification, vegetation mapping and many other purposes.

Each set represents a distinct data acquisition project with unique characteristics. Acquisition dates range from 2002 to 2012 and a variety of agencies and/or partnerships sponsored these missions – details can be found in the project specific metadata. Differences include the instruments used to acquire the data, processing software, accuracy, point spacing, format, projection, tiling schemes, and availability of derivative products such as contours and breaklines. Point and raster data are available for each project area. The point data are in ASCII text files storing XYZ coordinates, binary LAS files, or bare-earth TINs. The rasters are GeoTiffs. The horizontal datum for all data is NAD83; the vertical datum is NAVD88.

View Project Area Index Map  (based on the LiDAR Index layer).
(Links to detailed index maps of each project area are found on each DEM download page.)

The following table summarizes data for the projects and contains links to download DEMs and metadata:
(*** see note below about downloading data in Internet Explorer)

Year / Project Name	Acquisition Dates	Projection / Units	DEM Size ** / Resolution	Point Size ** / Format	Full Metadata *
2002 Boston Area	April, 2002	MA State Plane Meters	3.16 GB 1 m [Download]	12.8 GB ASCII	.ZIP 40k
2004 Hampden County	May-July, 2004	MA State Plane Feet	118 MB 10 ft [Download]	804 MB ASCII	.ZIP 6MB
2004 Southeast Pilot	April 30, 2004	MA State Plane Meters	136 MB 2 m [Download]	899 MB LAS, TIN	.ZIP 3MB
2005 Blackstone River	NA	MA State Plane Feet	289 MB 8 ft [Download]	9.37 GB TIN	Text 1k
2006 Bristol County	Nov. 10-26, 2006	MA State Plane Feet	394 MB 4 ft [Download]	11.2 GB ASCII, TIN	.ZIP 26MB
2006 Plymouth Co. S.	Nov. 10-26, 2006	MA State Plane Feet	457 MB 4 ft [Download]	13.7 GB ASCII, TIN	.ZIP 26MB
2006 Shawsheen River	Dec. 16, 2006	MA State Plane Meters	491 MB 1 m [Download]	415 MB LAS	.ZIP 14k
2009 City of Boston	Nov. 9-10, 2009	MA State Plane Feet	7.6 GB 3.28 ft [Download]	9.6 GB LAS	Text 1k
2010 Concord River	Dec. 2-12, 2010	UTM Zone 19N Meters	2.95 GB 1 m [Download]	28.8 GB LAS	.ZIP 60MB
2010 Charles River	Dec. 2-11, 2010	UTM Zone 19N Meters	1.93 GB 1 m [Download]	19.4 GB LAS	.ZIP 86MB
2010 Quincy	Dec. 17, 2010	UTM Zone 19N Meters	721 MB 1 m [Download]	3.1 GB LAS	.ZIP 33MB
2010 Narragansett River	Dec. 8-10, 2010	UTM Zone 19N Meters	1.86 GB 1 m [Download]	19 GB LAS	.ZIP 29MB
2010 Blackstone River	Dec. 15-17, 2010	UTM Zone 19N Meters	1.18 GB 1 m [Download]	10.3 GB LAS	.ZIP 77MB
2010 Dukes County	NA	MA SPC Island Zone Feet	1.04 GB 1 m [Download]	1.5 GB ASCII, TIN	.ZIP 11MB
2010 Nantucket	NA	MA SPC Island Zone Feet	434 MB 1 m [Download]	176 MB ASCII, TIN	.ZIP 15MB
2011 Nashua River	May 6-7, 2011	UTM Zone 19N Meters	3.14 GB 1 m [Download]	26.7 GB LAS	.ZIP 69MB
2011 Northeast	Winter-Spring 2011	UTM Zone 19N Meters	17.5 GB 1 m [Download]	184 GB LAS	.ZIP 18MB
2012 Merrimack Watershed	Nov. 2011-Jan. 2012	UTM Zone 19N Meters	1 GB 1 m [Download]	4.4 GB LAS	.ZIP 26MB
2012 Hudson-Hoosic and Deerfield	Mar 20-Apr. 30, 2012	UTM Zone 18N Meters	2.35 GB 2 m [Download]	6 GB LAS	.ZIP 5MB

View/download a more detailed version of the above table  , including information on accuracy and point spacing.

Also available: April 2009 LiDAR and Ortho Imagery for the town of Amherst.

* Metadata .ZIP files include an overview text file and various documentation (PDFs, Word docs, and text files on acquisition, processing, QA, etc.) as delivered to MaassGIS. Metadata varies by project area.
** DEM and Point file sizes represent the sum of all files as bzip2 or laz compressed archives for a project area and are provided to aid in ordering the data. The data file sizes will be larger when uncompressed, which is necessary in order to use the files in GIS and other software. Files sizes of individual rasters differ among and within project areas. These file sizes are listed on each project area's raster download page.
Click on the [Download] links above to download DEM tiles for that project area.

Notes:
LiDAR flight lines are frequently aligned with the terrain.
For flood mapping, LiDAR data may only have been processed near rivers and streams or along coastlines.

To learn more about LiDAR, a good place to start is the USGS Center for LIDAR Information Coordination and Knowledge.

What MassGIS Distributes

MassGIS is distributing two products:

• Ground-classified .las files or bare-earth classified points represented by text files in XYZ format. (Nantucket text files are in XYZI format, where "I" represents the (uncalibrated) intensity of the LiDAR return.) LAS files represent a "point cloud", the three-dimensional composite of all returns from all laser pulses as determined from the aerial mission. These returns are analyzed to identify those that were probably reflected from the ground. The LAS files may be ordered on DVD or customer-provided hard drive (in the Digital Data Products > Elevation Data section).
  
  The .las files for the 2012 Merrimack and Hudson-Hoosic and Deerfield areas have been compressed into .laz files. A .laz extension indicates that the LAS (.las) file has been compressed into a much smaller LAZ file with LASzip. LAZ files are only 7-20 percent of the original file size, and the process is completely lossless. LASzip is part of LAStools, a free download from http://rapidlasso.com/. All LAStools read, process, and write the compressed format directly without having to first decompress the file.
• Bare-earth Digital Surface Model (DSM) rasters (aka DEMs - digital elevation models) in GeoTIFF format, tiled to correspond to the .las or .xyz files. These data were either provided to MassGIS as a project deliverable, or created by MassGIS from the ground-classified points. In this context, DSM refers to a "bare earth" digital elevation model raster dataset without buildings or vegetation. In cases where MassGIS created a raster DEM where none was delivered, any return with a .las GROUND classification was converted to a multipoint feature class, and then a Terrain in ESRI ArcGIS 10. Breaklines representing various water features were included in the Terrain where available. The Terrain was then linearly interpolated to a floating-point raster (ERDAS Imagine .img file format). Finally, this large image dataset was “diced” into GeoTIFF tiles appropriate for each project. The raster data may be downloaded (see links for each project area in the table above) or ordered on DVD or customer-provided hard drive (in the Digital Data Products > Elevation Data section).
  
  *** Note about downloading .bz2 files in Internet Explorer:
  
  MassGIS recommends using the Firefox, Chrome, or Safari web browsers to download the bzip2 compressed GeoTiff raster DEMs. If using Internet Explorer, when you click on a download link IE may attempt to display the binary contents of the file rather than prompt for downloading it. As a workaround in IE, right-click a .bz2 file, choose Save Target As..., and in the Save As dialog, choose "All Files" from the 'Save as type' dropdown. Then, in the "File name" box, change the .htm extension to .bz2 and click Save. When using Firefox, Chrome or Safari (the three browsers in addition to IE that MassGIS tested), you simply need to click on the .bz2 link and you will be prompted to download the file.

Using the DEMs in GIS Software

Unzipping .bz2 Files

The GeoTiff DEMs are provided for download in bzip2 compressed file format. The .bz2 files were created using the free and open source bzip2 1.0.6 software. Each .tif file must be extracted from its .bz2 file by using a compression utility such as the free and open source 7-Zip and bzip2 software, or any tool that recognizes the .bz2 file format. Most Linux and Unix systems have bzip2 installed or have it included in their installation media.

Creating Pyramids and Statistics

To keep the downloads' file sizes as small as possible, the .bz2 downloads do not include accompanying pyramid or statistics files for the GeoTiffs. When loading the .tif into ArcMap, for example, the user may be prompted to build pyramids in order to speed image display.

More importantly, when first displaying the image it may appear as a single shade of gray, an artifact of the image not having statistics. To correct this, the image must be stretched (in the layer's Properties > Symbology tab >Stretch section). Since image stretching requires statistics, the user may be prompted to compute statistics when choosing a stretch method. When applied, the image will then display as expected. See the document LiDAR Image Stretching  for illustrated details.

Last Updated 5/16/2013