Hanoi-Vietnam: Determination of the accuracy of National Topographic Maps at scales of 1:2,000 and 1:5,000

According to the regulations, the National Topographic Maps at scales of 1:2,000 and 1:5,000 display the characteristics of topography, physical features, borders, administrative boundaries, and place names on the mainland, islands, and archipelagos. These maps are constructed according to national technical standards and norms at scales of 1:2,000 and 1:5,000 within the national coordinate system and national elevation system to be uniformly used across the country.

Illustrative image (source: internet)

The accuracy of the National Topographic Maps at scales of 1:2,000 and 1:5,000 are determined according to Article 5 of Circular 19/2019/TT-BTNMT as follows:

- The mean square error in the plane of geographic objects displayed on the national topographic map according to the establishment scale should not exceed the following values:

• 0.5 mm on the map for plain areas, hills, and low mountains;
• 0.7 mm on the map for high mountainous areas and obscured regions.

- The mean square error in the height of geographic objects displayed on the national topographic map should not exceed the values specified in Table 2 below:

- The limit errors in plane and height of geographic objects are 2.5 times the mean square error in plane and height of geographic objects displayed on the map. When checking, the maximum error should not exceed the limit error. The number of instances with an error greater than 2.0 times the mean square error in plane and height of geographic objects displayed on the map should not exceed 5% of the total checked instances. In all cases, the errors should not be systematic.

According to the Circular, the National Topographic Maps at scales of 1:2,000 and 1:5,000 includes both digital format national topographic maps and national topographic maps printed on paper. The digital format national topographic maps can be in one of the formats GeoPDF, PDF, GeoTIFF, TIFF, EPS, ECW, JPEG and accompanied by a metadata file.

More regulations may be found in Circular 19/2019/TT-BTNMT effective from January 23, 2020.

Thu Ba

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