New Hypsometric Ramps for OCAD DEM Based Maps

Hypsometric tinting ramps expand

OCAD DEM colour ramps image

OCAD DEM colour ramps

The mapper of smaller scale maps such as trail maps, may be interested to know that three new colour ramps have been added to the hypsometric tinting choices in a coming OCAD update. One ramp allows choice of colours in up to 10 bands.
 

 

Brown – Yellow colour ramp

Brown - Yellow hypsometric image

Brown – Yellow hypsometric

Brown (high elevation) – Yellow (low) offers a ramp similar to that of the Sustrans UK touring cycle maps. It is easy on the eye yet effective. The ramp in the image is at 50m intervals on a 1:100,000 scale map (and like our Spa Country Explorer trail maps, it is printed on Pretex).

Research shows that many users of hypsometric tinted maps think that colours have meaning for ground content as well as elevation. For example a tint that has green at the lowest level implies to those users that the green also represents forest or farmland. Therefore there has been effort to avoid colour ramps that could give rise to such confusion.

On the full map of the Brown – Yellow image, the cartographers have added a green overlay for specific forest sections. Those are not large areas so it does work well. (See Shaded Relief website below for an article Evaluating Cross Blended Hypsometric Tints)

Red – Yellow colour ramp

Lerderderg Red-Yellow ramp image

Red-Yellow hypsometric

While Brown – Yellow colour ramp tends towards subtle, Red – Yellow is striking yet not glaring. The ramp used in the image is per 100m on part of an 80km trail trial map. The yellow is the Lerderderg Gorge (VIC).

I also trialled showing 50m contours on this 100m ramp. It may well be useful for less expert mountain bike riders who may be more conscious of elevation change when planning trips.

Colour yourself purple

The Greyscale Interval colour ramp is very useful addition. It produces a greyscale 10 segment ramp with each segment at your specified contour interval.

Using an image processing tool you can select each greyscale level in the resulting TIFF background  file and change to a colour of your choosing.

After processing a segmented greyscale, I started up the ubiquitous IrfanView (free but well worth a donation). Sure enough, I found it had the ability to easily select a greyscale and change it to another colour. Below is the before and after image I generated using this process. Not a colour ramp you would use for real but you are welcome to add it to your art collection 🙂

Selectable hypsometric tints OCAD & post-OCAD image

Selectable hypsometric tints OCAD & post-OCAD

Further reading

For those interested in exploring hypsometric tinting specifically or shaded relief generally, then these two websites are good resources.

Shaded Relief website

Relief shading website Some superb hand drawn relief shading including an example produced during 1838-45. I learnt that DEM based relief shading is termed Analytical Relief Shading.

Jim’s Cartography website has some viewable maps that use relief shading effectively without including contours. Jim Lewis is a NZ  OCAD user.

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