#digital elevation model

𝗛𝗢𝗪 𝗧𝗢 𝗠𝗔𝗞𝗘 𝗔𝗡 𝗘𝗟𝗘𝗩𝗔𝗧𝗜𝗢𝗡 + 𝗛𝗜𝗟𝗟𝗦𝗛𝗔𝗗𝗘 𝗠𝗔𝗣 𝗪𝗜𝗧𝗛 𝗣𝗥𝗢𝗙𝗜𝗟𝗘𝗦 𝗜𝗡 𝗤𝗚𝗜𝗦

𝗦𝗧𝗘𝗣 𝟭: 𝗗𝗼𝘄𝗻𝗹𝗼𝗮𝗱 𝗘𝗹𝗲𝘃𝗮𝘁𝗶𝗼𝗻 𝗗𝗮𝘁𝗮

Go to 𝗨𝗦𝗚𝗦 𝗘𝗮𝗿𝘁𝗵 𝗘𝘅𝗽𝗹𝗼𝗿𝗲𝗿.

Search for your area of interest.

Download 𝗦𝗥𝗧𝗠 𝟭 𝗔𝗿𝗰-𝗦𝗲𝗰𝗼𝗻𝗱 𝗚𝗹𝗼𝗯𝗮𝗹 𝗗𝗘𝗠 tiles covering your region.

𝗦𝗧𝗘𝗣 𝟮: 𝗠𝗲𝗿𝗴𝗲 𝗗𝗘𝗠 𝗧𝗶𝗹𝗲𝘀 (𝗜𝗳 𝗬𝗼𝘂 𝗛𝗮𝘃𝗲 𝗦𝗲𝘃𝗲𝗿𝗮𝗹)

If you downloaded multiple tiles:

Open QGIS.

Go to 𝗥𝗮𝘀𝘁𝗲𝗿 → 𝗠𝗶𝘀𝗰𝗲𝗹𝗹𝗮𝗻𝗲𝗼𝘂𝘀 → 𝗕𝘂𝗶𝗹𝗱 𝗩𝗶𝗿𝘁𝘂𝗮𝗹 𝗥𝗮𝘀𝘁𝗲𝗿 (𝗩𝗥𝗧).

Select all DEM tiles.

Click 𝗥𝘂𝗻.

You now have a single seamless DEM.

𝗦𝗧𝗘𝗣 𝟯: 𝗖𝗹𝗶𝗽 𝘁𝗵𝗲 𝗗𝗘𝗠 𝘁𝗼 𝗬𝗼𝘂𝗿 𝗕𝗼𝘂𝗻𝗱𝗮𝗿𝘆

Open 𝗣𝗿𝗼𝗰𝗲𝘀𝘀𝗶𝗻𝗴 𝗧𝗼𝗼𝗹𝗯𝗼𝘅.

Search for 𝗖𝗹𝗶𝗽 𝗥𝗮𝘀𝘁𝗲𝗿 𝗯𝘆 𝗠𝗮𝘀𝗸 𝗟𝗮𝘆𝗲𝗿.

Input layer → Your DEM (or VRT).

Mask layer → Your district/region boundary.

Click 𝗥𝘂𝗻.

Now you have a clean elevation map for your area.

𝗦𝗧𝗘𝗣 𝟰: 𝗦𝘁𝘆𝗹𝗲 𝘁𝗵𝗲 𝗘𝗹𝗲𝘃𝗮𝘁𝗶𝗼𝗻 (𝗛𝘆𝗽𝘀𝗼𝗺𝗲𝘁𝗿𝗶𝗰 𝗧𝗶𝗻𝘁)

Right-click the clipped DEM → 𝗣𝗿𝗼𝗽𝗲𝗿𝘁𝗶𝗲𝘀 → 𝗦𝘆𝗺𝗯𝗼𝗹𝗼𝗴𝘆.

Choose 𝗦𝗶𝗻𝗴𝗹𝗲𝗯𝗮𝗻𝗱 𝗽𝘀𝗲𝘂𝗱𝗼𝗰𝗼𝗹𝗼𝗿.

Select a color ramp (e.g., green → yellow → brown).

Click 𝗖𝗹𝗮𝘀𝘀𝗶𝗳𝘆 → Apply → OK.

This creates the elevation color variati

𝗦𝗧𝗘𝗣 𝟱: 𝗖𝗿𝗲𝗮𝘁𝗲 𝗛𝗶𝗹𝗹𝘀𝗵𝗮𝗱𝗲

Open 𝗣𝗿𝗼𝗰𝗲𝘀𝘀𝗶𝗻𝗴 𝗧𝗼𝗼𝗹𝗯𝗼𝘅.

Search for 𝗛𝗶𝗹𝗹𝘀𝗵𝗮𝗱𝗲.

Input layer → Your clipped DEM.

Click 𝗥𝘂𝗻.

𝗦𝗧𝗘𝗣 𝟲: 𝗕𝗹𝗲𝗻𝗱 𝗛𝗶𝗹𝗹𝘀𝗵𝗮𝗱𝗲 𝘄𝗶𝘁𝗵 𝗘𝗹𝗲𝘃𝗮𝘁𝗶𝗼𝗻

Right-click the hillshade layer → 𝗣𝗿𝗼𝗽𝗲𝗿𝘁𝗶𝗲𝘀.

Under 𝗦𝘆𝗺𝗯𝗼𝗹𝗼𝗴𝘆, change 𝗕𝗹𝗲𝗻𝗱𝗶𝗻𝗴 𝗠𝗼𝗱𝗲 to 𝗠𝘂𝗹𝘁𝗶𝗽𝗹𝘆.

Click 𝗔𝗽𝗽𝗹𝘆 → OK.

Now you have realistic terrain relief.

𝗦𝗧𝗘𝗣 𝟳: 𝗖𝗿𝗲𝗮𝘁𝗲 𝗘𝗹𝗲𝘃𝗮𝘁𝗶𝗼𝗻 𝗣𝗿𝗼𝗳𝗶𝗹𝗲 𝗟𝗶𝗻𝗲𝘀

Create a new 𝗟𝗶𝗻𝗲 𝗦𝗵𝗮𝗽𝗲𝗳𝗶𝗹𝗲 layer.

Digitize straight lines across areas of interest.

Style them:

Red color

Dashed or dott

Slightly thicker width

These will be your cross-section lines.

𝗦𝗧𝗘𝗣 𝟴: 𝗚𝗲𝗻𝗲𝗿𝗮𝘁𝗲 𝗘𝗹𝗲𝘃𝗮𝘁𝗶𝗼𝗻 𝗣𝗿𝗼𝗳𝗶𝗹𝗲𝘀

Go to 𝗩𝗶𝗲𝘄 → 𝗘𝗹𝗲𝘃𝗮𝘁𝗶𝗼𝗻 𝗣𝗿𝗼𝗳𝗶𝗹𝗲.

In the Elevation Profile window:

Click 𝗔𝗱𝗱 𝗟𝗮𝘆𝗲𝗿𝘀 → Add your DEM.

Click 𝗖𝗮𝗽𝘁𝘂𝗿𝗲 𝗖𝘂𝗿𝘃𝗲 → Click along one of your profile lines.

Under 𝗦𝗲𝘁𝘁𝗶𝗻𝗴𝘀, set 𝗗𝗶𝘀𝘁𝗮𝗻𝗰𝗲 𝗨𝗻𝗶𝘁𝘀 = 𝗞𝗶𝗹𝗼𝗺𝗲𝘁𝗲𝗿𝘀.

Your elevation graph will appear.

𝗦𝗧𝗘𝗣 𝟵: 𝗔𝗱𝗱 𝗣𝗿𝗼𝗳𝗶𝗹𝗲𝘀 𝘁𝗼 𝗣𝗿𝗶𝗻𝘁 𝗟𝗮𝘆𝗼𝘂𝘁

Open 𝗣𝗿𝗼𝗷𝗲𝗰𝘁 → 𝗡𝗲𝘄 𝗣𝗿𝗶𝗻𝘁 𝗟𝗮𝘆𝗼𝘂𝘁.

Add your main map.

Click 𝗔𝗱𝗱 𝗘𝗹𝗲𝘃𝗮𝘁𝗶𝗼𝗻 𝗣𝗿𝗼𝗳𝗶𝗹𝗲 (bottom-left tools).

Draw the profile frame.

In the right panel → Click 𝗖𝗼𝗽𝘆 𝗙𝗿𝗼𝗺 𝗣𝗿𝗼𝗳𝗶𝗹𝗲.

Repeat for all cross-section lines.

𝗦𝗧𝗘𝗣 𝟭𝟬: 𝗙𝗶𝗻𝗮𝗹 𝗖𝗮𝗿𝘁𝗼𝗴𝗿𝗮𝗽𝗵𝗶𝗰 𝗧𝗼𝘂𝗰𝗵𝗲𝘀

In the Layout, add:

Grid (with coordinates)

North arrow

Scale bar

Legend

Title

Data source

Credits

Flood models reflect an actual land surface using DEM data. The amount of land that each grid cell in a DEM can represent is referred to as its spatial resolution. A grid cell that has a spatial resolution of 10 meters thus represents an actual land area that is 10 by 10 meters. The labels "low resolution" and "high resolution" are relative. A "lower" resolution dataset typically smoothes out topographic characteristics, while a "higher" resolution dataset implies considerably more preservation of land features (Environmental Systems Research Institute, Inc., 2016).

In the hydrological and hydraulic modeling sector, DEM resolutions typically range from 1000m to 2m or less (Vaze, Teng, & Spencer, 2010). Here, we restrict our discussion to the national-scale flood maps from JBA, whose resolution ranges from 30m to 5m.

During the flood modeling process, flood modelers must make many crucial decisions. We research the assumptions made to depict complicated natural phenomena; we gather, validate, and incorporate input data; we create and test models, and we critically evaluate the outcomes. The DEM is essential to this applied and unreliable science. Determining where floods are most likely to cause problems for people and property and estimating how water interacts with the environment depend on high-quality DEM data.

The precision and spatial resolution of the DEM affect the accuracy of forecasts of water depth (Vaze, Teng, & Spencer, 2010).

However, even while increased spatial resolution and accuracy frequently lead to better outcomes, these advantages cannot be taken into account separately, especially when taking into account how numerical flood models function. The physical processes of floods are represented by numerical models using many simulations, which, depending on the size of the area, may number in the hundreds of thousands or more. The higher the geographical resolution, the more complicated the models are, and the more computer resources, processing time, file size, data storage, and cost are required (Environmental Systems Research Institute, Inc., 2016).

The preservation of topographical landscape elements increases with increasing DEM resolution. This offers a clearer delineation of the floodplain, tiny streams, highways, and other restricted flow conduits that have a big impact on outcomes. High-resolution topographical data is becoming more widely available, although it's still not everywhere. These data frequently only cover nations and areas with significant populations and/or economic development. However, it makes sense to invest in them if there is a demand from customers and the market for higher resolution flood data as well as good quality and quantity of data.

JBA offers 5m-resolution high-resolution flood maps for the US, Continental Europe, the UK, and the Republic of Ireland. Figure 3 shows how the flood maps for downtown Miami have changed as a result of using better-resolution data. The 5m map depicts water movement in intricate urban regions, while the 30m map does not, even if both images show the general areas at risk from floods. The validation of our modeling results using data on past and present flood events support a better, more in-depth understanding of floods from high-resolution maps.

The combination of a number of factors allows us to meet the various requirements of clients despite the fact that flood modeling is a difficult science. Using higher-resolution resources has significantly improved the ability to assess flood risk in locations where we are confident in the quality and quantity of the input data, even if the resolution is not the only criterion for judging the quality of a dataset.

(2010, 44 x 30 inch, DEM, 3D CGI, pigment ink on rag paper, edition 7 + 2 EA)

(2010, 44 x 30 inch, DEM, 3D CGI, pigment ink on rag paper, edition 7 + 2 EA)

• Work Statement:

«Germania Flats» is a cycle of computer simulated aerial views of the Gulf of Naples with the Mt Vesuvius volcano and environs. A digital elevation model (DEM) is mapped with Lower East Side sidewalk textures and concrete graffiti and rendered in a 3D program.

The title refers to the cornice of two semi-detached houses on Houston and 2nd Avenue that spelled GERMANIA FLATS. The infamous Mars Bar was in the second building, which was demolished shortly after I completed this series.