Remotely-Sensed Data in ArcGIS Online
ESRI makes remotely-sensed data from a variety of sources directly available through ArcGIS Online. While this data is published as tile layers that cannot be used for complex analysis or symbolization, the app allows you filter scenes for specific dates and display scenes in a variety of band combinations. If your needs are limited to straightforward visualization, this data can save you the time, effort, and storage needed to download and process this data directly from sources like NASA or USGS.
Add the Data
Start a new Map in ArcGIS Online, click the Add button, Search for Layers in ArcGIS Online, and find one of these layers:
- Multispectral Landsat: Landsat 8 is the latest satellite in NASA's Landsat program, which has been gathering satellite imagery of the earth continuously since 1972 (NASA 2020). Landsat imagery has 30-meter spatial resolution.
- Sentinel-2 Views: Sentinel-2 is an Earth observation program from the European Space Agency (ESA) similar to NASA's Landsat (ESA 2020). Sentinel-2 data has 10-meter spatial resolution.
- USA NAIP Imagery: Natural Color: The National Agriculture Imagery Program (NAIP) is a USDA Farm Services Agency program that collects aerial imagery annually during the agricultural growing season in the continental US (USDA 2020). NAIP imagery spatial resolution ranges from 0.6 to 1 meter.
The video below demonstrates adding a Landsat layer.
Set The Image Display
ArcGIS Online provides a variety of different way of displaying the different bands available in the data sources above.
Click on the ellipsis (...) beside the layer, select Image Display, and under Renderer, choose from one of the following:
- Natural Color displays the red, green, and blue bands with a stretch of values that displays the data as it would appear to the naked eye.
- False Color Composite displays near-infrared as red, green as blue, and red as green. Plants reflect more near infrared than green, so this renderer causes plant-covered land to appear deep red. This makes it easier to see changes in plant health (NASA 2014).
- Agriculture displays shortwave IR-1 as red, near-IR as green, and blue as blue, with dynamic range adjustment applied. This causes vigorous vegetation to appear bright green, stressed vegetation to appear dull green, and bare areas to appear as brown.
- NDVI Color or NDVI Colorized displays normalized difference vegetation index (NDVI) on a spectrum of red or brown (low NDVI) to green (high NDVI). NDVI is a ratio of (near_infrared - red) / (near_infrared + red), which gives a range of -1 (no vegetation) to 1 (high vegetation).
- NDMI Colorized displays normalized difference moisture index with a color map that makes wetlands and moist areas appear blue, and dry areas appear deep yellow and brown. NDWI is similar to NDVI, but with different bands in the formula: (near_infrared - shortwave_infrared1) / (near_infrared + shortwave_infrared1).
The video below demonstrates adding changing the renderer to NDVI colorized:
Remotely-sensed data is continuously captured as the satellite flies over the face of the earth, but it is commonly cut into more-manageable blocks of rasters called scenes for distribution and analysis.
By default, layers display an overview mosaic of scenes from different dates that are stitched together to show the extent covered by the layer and what the scenes generally look like.
To select a specific scene from a specific time (or range of times) for a specific area:
- Zoom in on the desired location. You can use the search bar to find specific locations.
- Click the ellipsis (...) beside the layer in the Contents pane and select Image Filter.
- The Attribute box allows you to select scenes that fit specific criteria. Using the default acquisition date gives you a slider to select from the available range of dates.
- The Image Filter Results box then shows you the scenes within that range of dates for your specific location. Rolling your mouse over the different search result listings will outline the extent on the map.
- You can click to select the scenes you wish to display, then click Add As a New Layer to add the scenes as a tile layer to the map.
The video below demonstrates selecting scenes for Maricopa County (Phoenix), Arizona:
Provide Geographic Context
Because the data layers obscure the base map, you may want to add some features to provide geographic context that indicates where the data is actually located.
You can use filtered feature layers with no fill to outline areas.
For this example, we use the ArcGIS Online USA Counties layer with a filter and hollow symboloty display the outline of Maricopa County, which contains Phoenix.
Add Labels With Map Notes
If you want to label specific features, you can find them on the base map and annotate them with Map Notes.
This video shows how to add map notes labels.
Save and Share Your Map
Other Notable Raster Layers
National Urban Change Indicator (NUCI)
The National Urban Change Indicator (NUCI) uses Maxar’s PCM, a change detection system using Landsat scenes, to detect persistent changes to the landscape resulting from urban development. The NUCI 2016 layer provides a history of change areas on an annual basis from 1987 through 2016. This layer can be useful for research into changes in city form and urban sprawl.
Earth at Night (2016)
NASA's Black Marble project provides visualizations of the earth at night. Like the NUCI, it is useful for visualizing the extent of cities.