Frequently Asked Questions
Mapping, Remote Sensing, and Geospatial Data
The USGS provides the mapping and digital geospatial foundation for the Nation.
Browse Mapping, Remote Sensing, and Geospatial Data science related to:
• US Topo
Once you've gathered as many facts about family history and customs as possible, turn to maps to uncover more specific information or to solve historical mysteries.
In the United States, birth, death, property, and some other kinds of records are normally kept by county governments. If you can name the place where an ancestor lived, new or old...
A diagram at the bottom of most USGS topographic maps shows three north arrows--true north, grid north, and magnetic north--and the angles between them. Some maps, especially very old maps, do not have this diagram.
Example of north arrows from US Topo map. Star is True north, GN is Grid north, MN is Magnetic north.
(Public domain.)
True...
A USGS topographic map is usually named for the most prominent feature within the bounds of the map, which is frequently a community. Most topographic maps are named for the most centrally located, well-known, and/or largest community identified on the map.
If the community for which the map should be named falls on two or more maps, a directional...
Landsat 7 ETM+ SLC-off data refers to all Landsat 7 images collected after May 31, 2003, when the Scan Line Corrector (SLC) failed. These products have data gaps, but are still useful and maintain the same radiometric and geometric corrections as data collected prior to the SLC failure.
See the Landsat 7 website for information about the SLC-off...
Data acquisition requests are not available to the public. The Landsat 8 and Landsat 7 satellites each acquire data on a continual basis in accordance with their respective Long Term Acquisitions Plans.
The Landsat Acquisitions page has calendars and information about daily schedules.
Learn more:
Landsat 8 Long Term Acquisitions Plan
Landsat 7...
Remote sensing is the process of detecting and monitoring the physical characteristics of an area by measuring its reflected and emitted radiation at a distance (typically from satellite or aircraft). Special cameras collect remotely sensed images, which help researchers "sense" things about the Earth. Some examples are:
Cameras on satellites and...
Light Detection and Ranging (lidar) is a technology used to create high-resolution models of ground elevation with a vertical accuracy of 10 centimeters (4 inches). Lidar equipment, which includes a laser scanner, a Global Positioning System (GPS), and an Inertial Navigation System (INS), is typically mounted on a small aircraft. The laser scanner...
Yes, there is a plan to scan and digitize all rolls of film. The plan is to first scan all rolls of film that are in danger of decay from vinegar syndrome and then scan everything else. Science and customer requirements are also reviewed on a regular basis, but a formal, online schedule is not available.
Learn more:
USGS EROS products overview...
The U.S. Geological Survey (USGS) Earth Resources Observation and Science Center (EROS) can only certify that the product downloaded through our website is an authentic reproduction of an official record of the government that is in the legal custody of the USGS EROS.
See the standard Authenticity of Digital Imagery document.
The ability to see specific items in an aerial image is mostly a function of scale and resolution. The following aerial photography products all have a resolution of 1 meter or better, so you should be able to see an object the size of a house:
High Resolution Orthoimagery (HRO)
National Agriculture Imagery Program (NAIP) imagery
Digital...
Many image processing programs (ERDAS IMAGINE®, PCI Geomatica®, ENVI®, IDRISI®, etc.)* can import a variety of image formats, including the GeoTIFF files of Landsat data.
Free Multispec software that is included with the USGS lesson plan Tracking Change Over Time can be used for limited spectral analysis.
To view Landsat scenes without using...
A number of artifacts and anomalies can happen to any remote sensing data. Banding, dropped scan lines, and detector failures are only a few of the anomalies that can be seen in Landsat data. Go to Landsat Known Issues for details about anomalies that have been discovered and investigated.