Digital Models

Creating Terrain Digital Models to Provide Increased Business Intelligence

Digital Models

Digital Elevation Model (DEM), Digital Surface Model (DSM) and Digital Terrain Model (DTM) are three commonly implemented geospatial features generated with UAV mapping systems. Each data product delivers different elevation values as each model uses different methodologies. Elevation values from a LiDAR point cloud come from features including bare-ground, power lines, tree canopies or buildings. Selecting the right elevation model for your project can be challenging that is why MODUS offers the following three common interpretations for these data products:

Digital Surface Models (DSM)

Digital Surface Model (DSM) that includes ground surface, vegetation and man-made objects DSM demonstrate the natural and artificial features on the Earth’s surface. Digital Surface Model may be useful for RF planning, landscape modelling, city modelling, visualization applications and more

Digital Elevation Models (DEM)

A Digital Elevation Model (DEM) is a representation of the elevation of the Earth’s surface above a certain datum (e.g. mean sea level) in digital form. This is achieved taking elevation measurements at regular or irregular spaced points over the Earth’s surface. Elevation Models are often confused with Digital Terrain Mapping where additional terrain markings are added to show the functionality of the terrain.

Digital Terrain Models (DTM)

Digital Terrain Model (DTM) typically augments a DEM, by including vector and breakline features of the natural terrain, such as rivers and ridges. A DTM may be interpolated to generate a DEM, but not vice versa.  DTM is often required for flood or ground rupture modeling, land-use studies, geological analysis. 

CANOPY HEIGHT MODEL (CHM)

TYPICAL USES FOR DRONE DEM/DTM MAPS:

3D Modeling

Volumetric Calculations

Contour Geneation

Powerline As-Built Surveys

Orthophoto Rectification

Flood Plain Mapping

DIGITAL MODEL TECHNICAL SPECIFICATIONS

Contours offered as a value-add to Standard and Enhanced Ortho products are:

2-foot Contours – Derived from 4-inch or 6-inch resolution Ortho
5-foot Contours – Derived from 12-inch resolution Sanborn Ortho

Contours from stereo imagery are aesthetically pleasing and highly accurate lines of equal elevation which are intended to correspond with the orthometric heights of the bare surface. The primary advantage of stereo imagery is the ability to extract cultural and geographic features in three dimensions such as buildings, roads and elevation contours. Stereo imagery is especially important for markets where accurate elevation data is not readily available.

Every fifth contour line is an Index Contour, distinguished using a heavier line style to enhance identification. All contour lines are solid and unbroken except where passing through dense ground cover, building, and under bridges. In these instances, the contour lines are still continuous, but they are attributed and displayed as broken/dashed lines.

Contours offered as a value add to Lidar products are:

6-inch Contours – Derived from High Precision Drone Lidar
1-foot Contours – Derived from High Density Drone Lidar
2-foot Contours – Derived from any Lidar

Contours are derived from a bare earth DEM surface, these contours best represent the high point density benefit of Lidar data. As an option, breaklines can be added to better depict edge of drainage feature, road edges and other sharp breaks or discontinuities in the terrain. Contours from Lidar are normally not smoothed, leading to a ragged appearance, this is not as cartographically as pleasing, however best represent the highly detailed surface. A gridding of the bare earth and smoothing can be applied at customer request to create a more traditional looking contour data set but reduces accuracy overall as a result.

Every fifth contour line is an Index Contour, distinguished using a heavier line style to enhance identification. All contour lines are solid and unbroken except where passing through dense ground cover, building, and under bridges. In these instances, the contour lines are still continuous, but they are attributed and displayed as broken/dashed lines.

Title goes here

contours are developed in accordance with the ASPRS contour guidelines for 1-foot, 2-foot, and 5-foot contour generation, and tested in accordance with NDEP-FEMA Appendix A guidelines. Accuracy testing in accordance with NDEP Version 1.0 May 10 Section 1.5.2.3 and 1.5.3.1 Fundamental Accuracy.

NMASEQUIVALENT CONTOUR INTERVAL

6-inch

1- foot

2- foot

5-foot

NMAS
VMAS 90 CONFIDENCE

0.2 – foot

0.5- fooot

1.0-foot

2.5-foot

NSSDA
RMSEZ

0.15-foot or 4.12 cm

0.30-foot or 9.925cm

0.61-foot or 18.25 cm

1.52-foot or 46.3cm

NSSDA
ACCURACY 95%

0.30-foot or 9.12 cm

0.60-foot or 18.25 cm

1.19-foot or 36.3 cm

2.98-foot or 90.8 cm

Relationship between Horizontal Resolution and Vertical Accuracy (ASPRS 2001) NDEP Section 1.3.8.2

Map datasets compiled at 1″ = 100′with 1′ contours: Comparable to DTMs with post spacing of 1 meter.

Map datasets compiled at 1″ = 200′with 2′ contours: Comparable to DTMs with post spacing of 2 meter.

Map datasets compiled at 1″ = 500′with 5′ contours: Comparable to DTMs with post spacing of 5 meter.

ORDERING INSTRUCTION (add deliver formats)

CONDITIONS

  • Topographic Maps price catalog is subject to change

  • Order acceptance subject to MODUS approval

  • High relief and dense terrain topo maps areas subject to MODUS approval

  • Product is warranted for 90 days as defined in the End User License agreement

  • Shipping and handling fees may apply

DELIVERY FORMATS

  • .dwg (AutoCAD)

  • .dxf (Drawing exchange)

  • .shp (ESRI)

Are you ready to get started with MODUS Maps?

For More Information or to Order MODUS Digital Modeling Products or Services,

Call MODUS Customer Service,

Contact Us by Email at Info@MODUS-Ai.COM, or

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