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What are national map accuracy standards?
In 1941, the U.S. Bureau of the Budget issued the “United States National Map Accuracy Standards,” which applied to all Federal agencies that produce maps. On a map with a contour interval of 10 feet, the map must correctly show 90 percent of all points tested within 5 feet (1.5 meters) of the actual elevation.
Why is the national map accuracy standards important?
The National Map Accuracy Standard (NMAS) provides insurance that maps conform to established accuracy specifications, thereby providing consistency and confidence in their use in geospatial applications.
What is USGS TNM?
The National Map Viewer (TNM Viewer) is the one-stop destination for visualizing all the latest National Map data. Let’s make MY MAP!
How accurate are USGS topo maps?
Turns out, USGS topo maps use the National Map Accuracy Standards. This means that 90 percent of the horizontal points tested by field survey teams are accurate to within 40 feet. Vertical points, to within half a contour line, or five feet, based on standard 7.5 minute, 10-foot contour lines. So, yeah.
What are accuracy standards?
A Accuracy Standards The accuracy standards help ensure that a student evaluation will produce sound information about a student’s learning and performance. A2 Defined Expectations for Students The performance expectations for students should be clearly defined, so that evaluation results are defensible and meaningful.
What is map accuracy?
The closeness of results of observations, computations, or estimates of graphic map features to their true value or position. Mapping accuracy standards generally are stated as acceptable error and the proportion of measured features that must meet the criteria.
What is USGS elevation?
The USGS 3D Elevation Program (3DEP) announces the availability of a new dynamic map service. The dynamic platform supports the exploration of Digital Elevation Models (DEMs) for the US and territories at a mixture of scales, including 1 meter DEMs.
What is elevation map?
The distinctive characteristic of a topographic map is the use of elevation contour lines to show the shape of the Earth’s surface. Elevation contours are imaginary lines connecting points having the same elevation on the surface of the land above or below a reference surface, which is usually mean sea level.
Does a topographic map show elevation?
Topographic maps are a detailed record of a land area, giving geographic positions and elevations for both natural and man-made features. They show the shape of the land the mountains, valleys, and plains by means of brown contour lines (lines of equal elevation above sea level).
Are GIS maps accurate?
What is the accuracy of the parcel data? The accuracy of the property lines varies depending on different factors. In general the newer a subdivision, the more accurate the mapped lines. In a newer subdivision, past 5 years or so, the lines are probably within 5 feet +/- of where they actually exist.
Why is accuracy important in surveying?
Accuracy is extremely important when it comes to surveying and engineering and there are an abundance of factors that can affect the measurements being exactly right. One mistake and you can throw off the design plans pretty quickly. And our surveyors hate upsetting our engineers….
Which method of survey is most accurate?
In-person interviews are by far the most personable approach and can create trust and cooperation from respondents. The best interviewers will be able to read non-verbal cues to better direct the interview. It is also the best way to perform interviews that may involve sensitive topics.
What was the national standard for spatial data accuracy?
The National Standard for Spatial Data Accuracy was developed by the FGDC ad hoc working. group on spatial data accuracy, with the intent to update the United States National Map Accuracy. Standards (NMAS) (U.S. Bureau of the Budget, 1947).
What are the vertical accuracy standards for maps?
The vertical accuracy standard requires that the elevation of 90 percent of all points tested must be correct within half of the contour inter- val. On a map with a contour interval of 10 feet, the map must correctly show 90 percent of all points tested within 5 feet (1.5 meters) of the actual elevation.
Why are National Geospatial program standards and specifications important?
Standards and specifications are essential to facilitate the development and sharing of geospatial data and products. National Geospatial Program (NGP) standards and specifications define requirements to ensure that all maps and data prepared by NGP, in support of The National Map, are consistent in accuracy, structure, format, style, and content.
When did the USGS begin to test accuracy?
In 1958, the USGS began systematicallytesting the accuracy of its maps.Presently, accuracy testing is performedon 10 percent of the mapping projects ateach contour interval as a method ofcontrolling overall quality. It is rare for a7.5-minute map to fail the test, but thishappens on occasion.