In this study, spot elevation
extracted from the toposheet were used as a reference elevation data to evaluate accuracy of the SRTM and ASTER DEMs.
For instance, the quality of the dataset "spot elevation
" affects the reliability of the spatial database in zones with strong slopes more than in smoothed zones.
When a plan indicates no specific spot elevations
, the contractor must rely on indications of slope direction.
Caltrans specifications require that 90 percent of spot elevations
be within one-fourth of a contour interval.
Mele Plain spot elevations
plotted on a modern 1:50,000 topographic map (contour interval 40 m) indicate that Mele Plain has a seaward slope of 0.008-0.009, showing that the present elevation of Mele Village and its environs is ~6 m ([+ or -] 1 m) above mean sea level.
The topographic data (contour lines and spot elevations
) are distributed in ESRI software--supported coverage and shapefile format.
Using contour lines and spot elevations
, the grading plan indicates the desired height of site elements and direction of slope.
are stations that are not part of the grid.
Architects will include spot elevations
on the project construction plans to ensure the new walkway slopes are uniform and accessible.
The two-person GIS program uses ARC/Info (Environmental Systems Research Institute [ESRI], Redlands, California) software to maintain about 300 individual data themes including detailed planimetric data such as: edge-of-pavement, structures, fence lines, waterways, and sidewalks; jurisdictional data, including parcel, zoning, school districts, etc.; geomorphic (landform) information including 2-ft topography and spot elevations
; and utility data such as water mains and laterals, sanitary and storm sewer systems, and gas pipe lines.
This results in a matrix of spot elevations
of about 67.8 m (223 ft) apart east-west and about 92.7 m (305 ft) apart north-south at the latitude/longitude of Wisconsin (about 45[degrees] N.
To help planetary geologists spot elevations
and depressions, vertical features have been highlighted through computer coloration, and their dimensions have been visually exaggerated 10-fold compared with horizontal features.