User:Pbsouthwood/Wikitravel dive site maps

Usage in article
Code  

Standard thumbnail size for dive site maps: width = 400 pixels. &mdash; Example shown with link to full resolution image at http://wikivoyage.org/upload/shared//1/15/Partridge_Point_reef_map.png in caption. This is not preferred as it does not take the user through the attribution and licensing information:

Further text scolling alongside image is disabled by   . This would not normally be used in the article. 

Code  

Second example is a default size thumbnail linked to the image description page on shared at http://shared.wikivoyage.org/wiki/Image:Partridge_Point_reef_map.png. This gives required attribution and licensing information directly, and a single click will take you to the full resolution image: 

Code  

Third example is linked to image in En: at http://en.wikivoyage.org/wiki/Image:Partridge_Point_reef_map.png Note colon in front of file name to suppress display. This also provides attribution information directly, and licensing or full resolution after one more click. However there are no apparent benefits compared to linking directly to the image description page on shared (example 2).

Layers

 * Annotation(en)
 * Spare parts

Standard Wikivoyage map colours

 * National parks: Fill 89c736ff
 * Major roads: Stroke ffffffff, width 1.6mm, Fill None
 * Minor roads: Stroke ffffffff, width 1.2mm, Fill None
 * Pedestrian paths: Stroke d0cb75ff, width 0.8mm, Fill None
 * Green spaces: Stroke 03857ff, width 0.05mm, Fill 89c736ff
 * Buildings: Stroke 7fb5b5ff or 000000ff, width 0.05mm, Fill bdb580ff
 * Water: Stroke: 7fb5b5ff, Fill 9ccec9ff
 * Street names: Fill 585858ff
 * Itinerary/route: Stroke ff0000ff, width 0.4mm, style dashed, beginning "Dot.m", middle "Arrow2send", end "Square.m"

Colours used on Pinnacle chart

 * Depth range 0 to 3m: Stroke none, Fill c6e5ecff
 * Depth range 3 to 6m: Stroke none, Fill a6d4dfff
 * Depth range 6 to 9m: Stroke none, Fill 8ac5d1ff
 * Depth range 9 to 12m: Stroke none, Fill 72b8c4ff
 * Depth range deeper than 12m: Stroke none, Fill 5aadbaff
 * Sand bottom Stroke none, Fill 5aad89ff?
 * Footpath: Stroke f5f1e9ff, style dashed, Fill none
 * Bare earth: Stroke none, Fill d89668ff
 * Vegetation (dark): Stroke none, Fill ??????ff
 * Vegetation (light): Stroke none, Fill ??????ff
 * Exposed rock: Stroke none, Fill ??????ff
 * Shadowed rock: Stroke none, Fill ??????ff
 * Legend box: Stroke 36779fff, Fill ffffffff
 * Title box: Stroke 1b4157ff, Fill d3e3e3ff
 * Title lettering: Stroke 44718aff. Fill 1b4157ff
 * Scale bar light: Stroke 1b4157ff, Fill d3e3e3ff
 * Scale bar dark: Stroke 1b4157ff, Fill 456980ff

Colours used on Partridge Point chart

 * Reef depth range 0 to 3m: Stroke none, Fill c6e5ecff
 * Reef depth range 3 to 6m: Stroke none, Fill a6d4dfff
 * Reef depth range 6 to 9m: Stroke none, Fill 8ac5d1ff
 * Reef depth range 9 to 12m: Stroke none, Fill 72b8c4ff
 * Reef depth range 12 to 15m: Stroke none, Fill 5aadbaff
 * Reef depth range 15 to 18m: Stroke none, fill 46a4adff
 * Reef depth range greater than 18m: Stroke none, fill 3498a0ff
 * Sand bottom all depths: Stroke none, Fill 5aad89ff
 * Kelp forest overlay: Stroke 878900ff, Fill 5b3b0079
 * Granite boulders above sea level: Stroke none, Fill c8c8c8ff
 * Granite boulders highlights: Stroke none Fill e3dbdbff
 * Granite boulders half tide/shadow: Stroke none, Fill 808080ff
 * Intertidal land: Stroke none, Fill 918abf
 * Land: Stroke none, Fill c8b7b7ff
 * Bush: Stroke none, Fill 6f916fff
 * Roadside gravel shoulder: Stroke none, Fill ffccaaff
 * Road tarmac: Stroke none, Fill 483737ff
 * Legend box: Stroke 36779fff, Fill ffffffff
 * Title box: Stroke 1b4157ff, Fill d3e3e3ff
 * Title lettering: Stroke 44718aff. Fill 1b4157ff
 * Scale bar light: Stroke 1b4157ff, Fill d3e3e3ff
 * Scale bar dark: Stroke 1b4157ff, Fill 456980ff

Colours used on Klein Tafelberg Reef chart

 * Reef depth range 0 to 3m: Stroke none, Fill c6e5ecff
 * Reef depth range 3 to 6m: Stroke none, Fill a6d4dfff
 * Reef depth range 6 to 9m: Stroke none, Fill 8ac5d1ff
 * Reef depth range 9 to 12m: Stroke none, Fill 72b8c4ff
 * Reef depth range 12 to 15m: Stroke none, Fill 5aadbaff
 * Reef depth range 15 to 18m: Stroke none, fill 46a4adff
 * Reef depth range 18 to 21m: Stroke none, fill 3498a0ff
 * Reef depth range 21 to 24m: Stroke none, fill 248c93ff
 * Reef depth range 24 to 27m: Stroke none, fill 158086ff
 * Reef depth range 27 to 30m: Stroke none, fill 0e7479ff
 * Reef depth range 30 to 33m: Stroke none, fill 07686cff
 * Reef depth range 33 to 36m: Stroke none, fill 045c5fff
 * Reef depth range 36 to 39m: Stroke none, fill 025052ff
 * Reef depth range greater than 39m: Stroke none, fill 004445ff
 * Sand bottom all depths: Stroke none, Fill 5aad89ff
 * Kelp forest overlay: Stroke 878900ff, Fill 5b3b0079


 * Legend box: Stroke 36779fff, Fill ffffffff
 * Title box: Stroke 1b4157ff, Fill d3e3e3ff
 * Title lettering: Stroke 44718aff. Fill 1b4157ff
 * Scale bar light: Stroke 1b4157ff, Fill d3e3e3ff
 * Scale bar dark: Stroke 1b4157ff, Fill 456980ff

Layers used on Klein Tafelberg Reef

 * Frame
 * Title and Legend
 * Text and features
 * Grid
 * Contour top
 * to


 * Contour bottom
 * Reef (or Sand)

Colours used in Coral Gardens (Oudekraal) chart

 * Dry granite: Stroke 000000ff, Fill d3ccc4ff
 * Rocky reef: Stroke 000000ff, Fill 79aabdff
 * Sand: Stroke none, Fill ded8cfff
 * Underwater sand patch: Stroke none, Fill 79ceceff
 * Kelp forest: Stroke ????????, Fill ????????
 * Route: Stroke ff0000ff, style dashed, Fill none

Fonts
DejaVu Sans Condensed

Special characters
Special characters can be entered by switching to Unicode mode. To toggle between normal and Unicode modes use Ctrl+U. Typing any non-hexadecimal character or Esc while in Unicode mode will return you to normal mode. Once in Unicode mode, you can enter by typing the two to four hexadecimal digits corresponding to the character you desire. Hit the Space bar to register the character and to start entering another Unicode character.

This only works when entering the text. Editing does not work. You can't come back to existing text and add special characters in this way.

Unicode for some useful characters:

 * Degree sign 00B0

File size
Wikivoyage Press recommended png file size 3008 x 1709 pixels

Surveying dive sites
There are several ways to survey a dive site, The GPS track method I use is medium tech, moderate hardware cost, intermediate labour intensity, and is unaffected by visibility &mdash; results are the same in good viz or bad. It is quite interesting to return to a site you have extensively mapped in poor visibility on a day when you can actually see large sections of the structure. There is a strong and entirely understandable deja vu as you recognize structures in full size 3D that were previously only known as lines on the map and rather dim and murky shadows.

Hardware and software
The hardware is a reasonably splashproof pocket GPS in a watertight plastic box on a closed cell foam Surface Marker Buoy (SMB to divers) The float must be buoyant enough to not be pulled under at any time, and low drag. I find 8kg positive buoyancy is adequate. I use a boat-shaped float carved from an old boogie board, covered with a layer of orange PVC tarpaulin cloth for visibility and toughness.

The GPS I use is a Garmin e-trex Vista, which does the job fine when it works. It has an annoying tendency to occasionally turn itself off without any obvious reason in the middle of a survey. What is important is that the GPS records a downloadable track, and that the trackpoints should be close together, so you dont lose too much detail. The GPS unit is housed in a small transparent topped Pelican box, which is nominally waterproof, but often leaks a bit, so the GPS needs to be reasonably waterproof.

The box has a piece of soft closed cell foam with a cutout to support the GPS so it does not rattle around and bang its buttons. The float is towed at the end of a regular diving DSMB reel or spool, whichever is more convenient. I have used both and both work well. A ratchet reel is slightly more convenient, but it is no big deal.

The track is downloaded to a PC using a cable and software provided with the GPS, and unneccessary track segments edited out before transferring the tracks to Google Earth. I make a copy of the track to clipboard and use photoshop to save it as a jpeg.

It is also possible to screensave from maximum resolution on Garmin map software and use these images as background to trace the contours. It helps to first open in a bitmap editor like Photoshop and erase the background to transparent. This procedure has the advantage that the images are to a consistant scale. Mark a few waypoints at convenient Lat/Long gridpoints before screensave to help position the image on the map in Inkscape

Import the jpeg into Inkscape, scale it as needed and trace the track onto your map.

Survey procedure
Depending on the type of dive site you may wish to draw contours, or outlines, or a combination. Positions of features can be recorded by digital camera if you set the time on the camera to exactly match the GPS. Depth profiles can be derived from a dive computer if it is also synchronised, but this can be time consuming for more than a few points. The easiest procedures are outlines and contours:
 * Contours &mdash; Choose a depth and swim around the feature with the reel held close to the surface of the feature at the chosen depth. It is advisable to stick to either clockwise or anticlockwise on a specific contour as this reduces confusion when splitting the tracks. Wherever possible swim at least the whole way around each feature and try to swim directly to the next feature to minimise confusion at the computer, or log times of starting and completing each contour on a slate. Also use a slate to record the time at point features, and be sure to stop there for at least 30 seconds. When you start a new contour at a different depth it can help to change from clockwise to anticlockwise ot vice versa. this makes the changeover point easy to identify.
 * Outlines &mdash; Swim along the edge you wish to outline at a speed which allows the GPS to produce a track with maximum resolution. You can get depths from a decompression computer if this is important, or just take spot readings on a slate. Record start and stop times for the track, and what it is. These things may seem utterly obvious at the time, but can become a bit vague afterwards, when you are trying to work out which track is which on the screen, and it is all very cluttered.

The line must be kept under tension to minimise the position error of the float. This is also proportional to speed and depth, and sea state can add noise to the signal, by moving the float as the waves pass. Wave/swell error will tend to be consistent and directional, and is surprisingly small with a low-drag float. Whenever convenient, it is helpful to get a cross check on your accuracy by measuring the same track on different days and different conditions.

Other methods
You can take photos and make sketches on a grid on a slate, estimating dimensions and using a compass for directions. This is not very accurate, but can be usable. Surfacing occasionally at major landmarks and taking bearings to fix their position is feasible but not efficient.

The high tech methods mostly involve surveys from a boat using side-scan sonar, which can give really high resolution, but the equipment is expensive and sensitive to bumping into large rocks.

Single or multibeam sonar/echo sounders linked to concurrent GPS input and suitable software can produce wireframe images of as high resolution as your equipment depth resolution and your patience or finances can tolerate. These methods require reasonable smooth surface conditions and do not involve diving. I am hoping to get data from this type of survey to combine with the GPS track data when they become available.