# Runway Watch - who could see the 1942 runway on Gibraltar

> A free, non-commercial 3D map of the Rock of Gibraltar, coloured by whether
> you could see the North Front runway from each spot in 1942, the year
> Operation Tracer secretly built a stay-behind observation cave inside the
> Rock. Orange: you could see it. Blue-grey: you could not. Click anywhere to
> test the view, switch between the runway of April 1942, November 1942 and
> July 1943, and hatch areas to exclude them from a search, saved as GeoJSON.

Live map: https://runwaywatch.gaborszabopoker.com/
Made by Gabor Szabo. Not affiliated with any government or military body.

## What a crawler should know

This is a WebGL application. The map is drawn at run time from data files;
index.html carries a description but not the map contents. If you want to know
what is on this map, read the data, not the page:

- /data/runway.json - the runway centreline, the three construction stages
  (1,150, 1,550 and 1,800 yd), the 82 target points every 20 m, and the model
  settings (eye 1.5 m, target 1 m above the runway, refraction k = 0.13)
- /data/viewshed.png - the result. North-up, the same 1275 x 1550 grid of
  4 m cells as the terrain. Red = April 1942, green = November 1942,
  blue = July 1943; value / 255 = share of that runway seen from 1.5 m above
  the cell. Sea and Spain are 0.
- /data/meta.json - the georeferencing: EPSG:25830, grid extent, cell size
- /data-sources.json - the dataset list with licences and official URLs

## What it found

Share of each part of the Rock (land above 30 m, 320.7 ha in all) that could
see at least some of the runway, and at least a quarter of it, for the runway
as built by November 1942:

- North end (36.8 ha): 84 % some, 68 % a quarter or more. The crest above the
  Great Siege Tunnels saw all of it.
- West side, facing the Bay (137.4 ha): 52 % some, 19 % a quarter or more,
  mostly the new western end pushed out into the Bay. Nowhere saw half.
- East side (62.3 ha): 6 % some, under 1 % a quarter or more.
- South (84.2 ha): 2 % some, nothing a quarter or more.
- Whole Rock: 34 % some (108 ha), 16 % a quarter or more (52 ha).

By July 1943 (1,800 yd) the west side rises to 79 % some and the whole Rock to
46 %. In April 1942 (1,150 yd) only 17 % of the Rock saw any of it.

The Operation Tracer cave site (about 410 m up, near the summit) sees none of
the runway at any stage on this model. The best spot within 100 m of it sees
3 to 4 % of the 1942 runway and 16 % of the 1943 one.

## Who it is for

- Historians of Gibraltar in the Second World War, of RAF North Front and of
  Operation Tracer
- Anyone searching for, or ruling out, places on the Rock with a view of the
  airfield
- Readers who want a georeferenced, reproducible line-of-sight result rather
  than a guess

## Where the data comes from

All of it is open, and all of it is credited on the page.

- HM Government of Gibraltar geoportal (geoportal.gov.gi): terrain model,
  about 21 % of the merged grid
- Spanish IGN PNOA-LiDAR MDT 5 m, CC BY 4.0 (scne.es): about 70 %
- Copernicus DEM GLO-30, (c) DLR e.V. 2010-2014 and (c) Airbus Defence and
  Space GmbH 2014-2018, provided under COPERNICUS by the European Union and
  ESA: about 10 %, filling gaps
- OpenStreetMap contributors, ODbL: today's runway centreline
- Runway stage lengths and the cave: Wikipedia (Gibraltar International
  Airport, RAF Gibraltar), the Royal Navy Research Archive page on North
  Front, and HM Government of Gibraltar press release 199/2018

## What it does NOT claim

- It is today's bare ground. Buildings, trees, wartime structures, spoil
  heaps and later quarrying are not in it, so in the town and on the lower
  slopes the real 1942 view was often worse than shown.
- The wartime extensions ran west into the Bay. The east end is taken as
  today's east end, and each stage is measured west from it. The stage ends
  are approximate.
- A spot counts as seeing the runway when the straight line from 1.5 m above
  the ground to a point 1 m above the runway clears the terrain. Haze,
  distance and what could actually be made out are not modelled.
- 2,996 of 3,000 random checks against an exact sightline test agreed; the
  rest are cells where the line grazes a ridge.

## Related

- Inside the Rock - Gibraltar today, tunnels and all,
  https://gibraltarmap.gaborszabopoker.com/
- 45,000 Years Ago - Neanderthal Gibraltar,
  https://gibraltar45k.gaborszabopoker.com/
- Through Deep Time - 200 million years of the Rock,
  https://gibraltargeology.gaborszabopoker.com/
- The Making of the Rock - a geological light show,
  https://gibraltarshow.gaborszabopoker.com/