This site provides browser-based geovisualization of high-resolution lidar digital terrain models (DTMs) across the six New England states (Maine, New Hampshire, Vermont, Massachusetts, Connecticut, and Rhode Island).
The purpose of this site is twofold: to help students learn about visual interpretation of landforms, and to support geosciences research in New England using digital elevation data.
To move around the map, click and drag (to pan), or use the scroll wheel or the zoom control at upper left (to zoom in or out).
If you want to jump to a particular street address or other location, enter it in the Search box at upper left. For example, to jump to the summit of Mt Moosilauke, type the name "Moosilauke" and choose either of the results in Benton, NH. If you try to jump to a location outside the extent of this map, it will only move to the edge of the map area.
To jump to a latitude/longitude location, enter the coordinates in decimal degrees, separated by a comma, like this: 44.023,-71.831 for latitude 44.023 degrees north, longitude 71.831 degrees west.
When first loaded, the page will be in dual-map mode, showing two linked maps at the left and right. Move either map and the other will follow. If you want to show the mouse cursor on both maps, choose Mouse tracking on the layer control menus for each map. If you prefer only a single large map (e.g., on smaller displays), change the Maps menu from "2" to "1" at upper right. (On large displays, you can also add a third map window.)
With multiple maps, the layers list box and other controls may take up a lot of space on your display. To temporarily hide the controls, click the Hide controls button at upper right.
The display can include a background layer (imagery or a basemap), a shaded relief layer, optional layers with hypsometric tint (elevation colors) or bedrock geology maps, a drawing layer, and several additional optional overlays.
Use the layer controls in each map window to show or hide each map layer. For the shaded relief, hypsometric tint, and geologic map layers, advanced settings can be controlled by clicking on the Settings button at top right.
Some map layers have popup windows - for example, with either shaded relief or hypsometric tint visible, clicking on the map will display the elevation at that point (it may take a few seconds for the popup to appear). The bedrock geology layer also has popup windows with details on rock types. If you want to turn off the popup windows, un-check the Show popups checkbox in the layers list.
There are two sources of elevation data for shaded relief: the US Geological Survey (USGS), and the six New England state GIS agencies (NE states). In most areas, they provide the same data, so if one appears to be slow loading, try using the other. As of this writing (2023) there are a few places where the USGS does not have full-resolution lidar coverage (e.g., southeast of Mt Moosilauke in New Hampshire), while there are also some minor gaps in the state lidar data.
The following shaded relief algorithms are available:
The opacity and illumination angles (azimuth and elevation) can be adjusted via the Settings button at top right:
"Hypsometric tint" refers to the use of a color gradient to represent a range of elevations; lower elevations are shown in one color and higher elevations in others.
See the note at the start of the previous section regarding sources of elevation data (USGS vs the six New England states).
The opacity and the elevation/color relationship for the hypsometric tint overlay can be adjusted via the Settings button at top right. The "Low" and "High" linear stretch settings will determine the lower and upper ends of the elevation range over which the color gradient is applied.
For the USGS elevation data, you can choose to use DRA ("dynamic range adjustment") rather than a specific linear stretch for the hypsometric tint. With DRA turned on, the color gradient will automatically be stretched over whatever range of elevations is found in the current map view. Note that if you move to areas with different elevations, the colors will change.
Additional overlays include bedrock geology, hydrography (lakes and rivers), and stream gages. Note that the bedrock geology layer is only visible up to zoom level 13, not at finer-scale zoom levels, and even at levels 12 and 13, the positions of map unit boundaries may not be reliable.
When the Show popups box is checked in a map's layers list, the bedrock geology layer will include highlighting and popup windows. Hovering the mouse over a bedrock polygon will show the polygon's bedrock code and highlight its outline in yellow; clicking on a polygon will open a popup with more details.
The Drawing tools are controlled on the left map (only). You can draw basic shapes - points, lines, circles, rectangles, and other polygons. To start drawing, click the Edit drawing layer checkbox on the layers menu. The drawing toolbar will appear at the left edge of the map; select one of the tools to start drawing shapes. Some important notes about drawing and editing:
To close the polygon, click the "Finish" label by the toolbar.
To edit an existing shape, click the Edit button on the lower part of the drawing toolbar. Then, click on a shape to start editing it, and click the "Save" label by the toolbar to save your edits.
Likewise, to delete an existing shape, click the Delete button on the lower part of the drawing toolbar. Then, click on a shape to delete it, and click the "Save" label by the toolbar to confirm the deletion.
When in dual-maps mode, the drawn features will show up on both maps, but can only be drawn, edited, or deleted on the left-hand map.
Use the buttons on the left map's layer control to Save or Clear the drawing layer. The file will be saved in GeoJSON format, and can be opened using QGIS or other desktop GIS software.
You can also load in existing points, lines, and polygons from your own data files in various formats. This can be done either with the Import file(s) / Browse button at the top right, or using drag and drop (select a file on your desktop and drag it onto the map). Note the following:
The file must have a suffix (extension) from this list: .csv, .txt, .geojson, .gpx, .kml, .topojson, .wkt. Files with other suffixes, or without a suffix, cannot be imported.
Files of type "csv" or "txt" must be comma-delimited, with a single header row of field names, followed by one row per data point. The fields must include "lat" and "lng". Here is an example:
| id | name | lat | lng |
| 1 | Dartmouth | 43.70316 | -72.288 |
| 2 | Moosilauke | 44.02342 | -71.83126 |
If you want to save the current map location (e.g., to share it with someone else), click the Share button at top right. The page address, including latitude, longitude, and zoom level, will be copied to the clipboard, and can then be pasted into an email, text message, or other link-sharing method.
Note that this saves most of the map settings, but does not share the drawing layer. To share drawn shapes, save your drawing layer as a GeoJSON file, then send it to the recipient, who can load it into their own copy of the map.
The lidar data may take time to load. When viewing data from the six New England states, one state may appear earlier or later than others.
The map defaults to using the USGS elevations database as the source for shaded relief and hypsometric tint. As noted above, both the USGS and NE States elevation datasets have advantages and disadvantages. It may occasionally be helpful to go back and forth between the two sources.
Finally, note also that the lidar data are from a mixture of sources both within and among states, acquired in different years with different spatial resolutions and other characteristics.
Currently, the bedrock geology layer is a composite of six individual state maps. Similar rock units may have different codes (and names, and colors) in neighboring states; in other cases, state geologic maps may disagree about the ages and characteristics of rock formations on opposite sides of their borders.
With over 1400 named bedrock units in the six New England states, it is not convenient to provide a tabular legend showing the symbols for all units, but unit codes and descriptions can be shown by clicking on unit polygons when in interactive mode (showing popups).
For any questions or comments, please contact Jonathan Chipman at Dartmouth College.
Design
Jonathan W. Chipman, Citrin Family GIS/Applied Spatial Analysis Lab. Department of Geography and Department of Earth Sciences, Dartmouth College, Hanover NH 03755 USA.
Data sources
Maine lidar data and bedrock geology from Maine GeoLibrary.
New Hampshire lidar data and bedrock geology from NH GRANIT.
Vermont lidar data and bedrock geology from Vermont Center for Geographic Information (VCGI).
Massachusetts lidar data from (MassGIS) via ArcGIS Online - layer info.
Connecticut lidar data from UCONN CT-ECO.
Rhode Island lidar data from Rhode Island State Enterprise GIS (RISEGIS) - layer info.
Vector hydrography data from the USGS National Hydrography Dataset (NHD).
Stream gage locations from many sources, compiled by Esri in this service.
Map placenames are provided by CARTO, based on data from OpenStreetMap, © OpenStreetMap contributors.
Background layers (imagery and basemaps) are from Esri (© Esri — Source: Esri, i-cubed, USDA, USGS, AEX, GeoEye, Getmapping, Aerogrid, IGN, IGP, UPR-EGP, and the GIS User Community), the US Geological Survey, and CARTO (© OpenStreetMap contributors).
Technology
The foundation of this site is the Leaflet Javascript API, an open-source platform for online map development.
Lidar data from individual states' Image Services are handled using the ESRI Leaflet API.
The geologic map data were exported to GeoJSON format from QGIS, processed into vector grid tiles using MapBox's Tippecanoe and MBUtil utilities, and then imported into Leaflet using Leaflet VectorGrid Tools.
Additional Leaflet plugins include Leaflet Control geocoder for geocoding, Leaflet Draw for drawing/editing tools, Leaflet Omnivore from MapBox for importing various file formats, and Leaflet CloneLayer for displaying copies of the drawing layer on both maps when in dual-map mode.