July 8, 2016: Data available for the entire state!
DEMs from 2015 are now available for Western Mass. (from the Quabbin Reservoir to the MA/NY border) and a portion of the Blackstone watershed, filling in large areas with no previous coverage and replacing some older areas. With the new data, DEMs at 1-meter pixel resolution are now available statewide.
A large section of the Western Mass. area contains Quality Level 1 (“QL1”) data, which contains points at a higher density (point spacing) than Quality Level 2 (“QL2”) data. Both QL1 and QL2 have the same vertical accuracy. 2015 LAS data are expected to be available for download from NOAA’s Data Access Viewer by late August.
These nine datasets contain Light Detection and Ranging (LiDAR) terrain files covering the entirety of Massachusetts. 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 2010 to 2015, 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 derived from the original LiDAR acquisition are available for each project area: The point data are in ASCII text files storing XYZ coordinates, binary LAS files (zipped as LAZ), or used to create bare-earth TINs; the raster DEMs (digital elevation models) are GeoTiffs or Erdas IMGs. The horizontal datum for all data is NAD83; the vertical datum is NAVD88. NOAA is now hosting most of our LAS data, which can be accessed for FREE through its Data Access Viewer.
Federal agencies are the primary contributors of the newer data. See the USGS' 3D Elevation Program page for an abstract and a link to a summary report for Massachusetts.
A free viewer is distributed by Fugro for viewing both LAS point files and the raster GeoTiffs, as well as shapefiles for referencing.
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)
Acquisition Dates Projection /
DEM Size ** /
Point Size ** /
Spring & Fall 2015 UTM Zone 18N &
ZIP 162 MB 2013-2014
Fall 2013 & Spring 2014 UTM Zone 18N &
ZIP 2 MB 2012
Nov. 2011-Jan. 2012 UTM Zone 19N
ZIP 26 MB 2011
Winter-Spring 2011 UTM Zone 19N
ZIP 18 MB 2011
May 6-7, 2011 UTM Zone 19N
ZIP 69 MB 2010
Dec. 15-17, 2010 UTM Zone 19N
ZIP 77 MB 2010
Dec. 2-11, 2010 UTM Zone 19N
ZIP 86 MB 2010
Dec. 2-12, 2010 UTM Zone 19N
ZIP 60 MB 2010
Dec. 8-10, 2010 UTM Zone 19N
ZIP 29 MB
To Download the DEMs for the above areas:
- Open OLIVER and use the Identify tools to select your area of interest.
- In the Identify results box click on the layer 'LIDAR Index (Most Current)'. The Feature details section will display the link for each tile you selected. Click on each link to download a .zip file containing the DEM.
- To download many images in a more automated way, click the 'Save all records as' dropdown and save to an Excel file. Then:
- Open Excel or a similar spreadsheet program, copy only the cells with the links and paste them into Notepad or other text editor and save as a text file.
- Download the free WinWGet software and load the text file into a new job. Run the job and all the zipped images will be downloaded to a folder you choose.
The illustrated instructions (PDF) on the download process file size 1MB for the LiDAR DEMs are identical as those for the 2013-14 Ortho Imagery.
View/download a more detailed table of the above , including information on accuracy and point spacing.
* 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 MassGIS. 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.
*** These DEMs are Erdas IMG files. All others are in Tiff format.
- 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 Lidar base specification report.
What MassGIS Distributes
MassGIS is distributing two products:
- Ground-classified .las files or bare-earth classified points represented by text files in XYZ format. 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. NOAA is now hosting most of our LAS data, which can be accessed for FREE through its Data Access Viewer.
- Bare-earth Digital Surface Model (DSM) rasters (aka DEMs - digital elevation models) in GeoTIFF and ERDAS Imagine formats, 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. In some cases, only the IMG files as delivered are posted for download. Free converters can be found online.
**** 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 and IMG 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 or .img 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 file sizes as small as possible, the .bz2 downloads do not include accompanying pyramid or statistics files for the GeoTiffs and IMGs. When loading the .tif or .img 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 in ArcMap). 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 8/19/2016