Cross-Sections and Components Finishing the drafting Last Class we got here: The plan view of the...

Cross-Sections and Components

Finishing the drafting

Last Class we got here:

The plan view of the cave looks great, walls are in, geology symbols and the details fill in the passage. It really is starting to look like the cave you surveyed

But we are missing information – not from the plan view, or graphical, but information about the cave that the viewer needs



We are missing Cross sections

Yet, much of the value of a cave map lies in how easily it can be understood by those who make use of it. The task of cartographer is not just to commit a cave to paper but also to make it easy for the viewer to interpret and make use of. In this light, the map user can immediately relate to a cross-section, since it mirrors what they see while inside the cave.Cross-sections, being drawn from the perspective of the caver, thus bridge this gap between symbols on paper and reality, and provide a recognizable reference for the end user. The different parts of an in-cave sketch combine not only to show what a cave does but what the cave is like, and cross-sections are the weapon of choice for describing the latter. (Jeff Bartlett Arkansas Underground 4/2009)



We are missing Feature or Passage names – to tell people where they are in the cave

We are missing Passage information, like ceiling height, depths of drops, and distance above/below entrance

This is all valuable information for someone moving through the cave



Cross SectionsWho doesn’t love cross sections?. Cross sections should be used liberally to explain what the passage is doing. However it can be a complex dilemma to get as much detail in without cluttering the map.Likewise, complex cross sections can add a lot to the map if done well.Cross sections should:

- either be scaled the same as the plan, or clearly called out as different

- Should have tic lines showing where they are being drawn in the cave

- Tic Lines should not contact map or cross section- Should show direction sketcher is facing when drawing and

up direction- Detail in cross section should match plan- Avoid gutless cross sections, don’t miss the complex areas!- Adding bedrock symbols can help cross sections stand out- Can be drawn Separate from plan – but must be located with

labels



Remember, in cave and out, only draw what you know…

If you don’t know where the ceiling or the floor are, make sure you denote this on the map

Water is too deep to touch bottom

Unknown Ceiling



There are many different ways to do cross sections



Cross Sections should be drawn right from the in-cave sketch just like all other components of the plan are.

This makes it important to do them correct in the cave. They should be to the correct scale, and have all the data needed in them.

Don’t be surprised if you draw more in-cave then you place on your final map, or if you need to move them to make the final map balanced. Draw them first, and then move them

Unused Cross section

Moved Cross section



I usually add a layer for each part of the cross section – walls, details and leader lines

I usually draw all the cross sections in my notes, and then move some to a hidden layer if they are not used



One reason to keep the cross-sections on a separate layer, is you might decide to flip the map. With the Cross sections separate you will just have to move them instead of rotating each one separately

In many cases you can even reuse the leader lines



The Cross-sections are a lower hierarchy (they should not stand out as much), so they should be a lower line weight then the walls

Here you can see that the walls are 2 point lines, and the cross sections are 1 point lines

Details can be .5 point.



Leader Lines (Tic Lines) have show several things, and have several parts

Leader Line

First, the leader line shows where in the cave the cross section is located. The line should be drawn right through the exact location that the section represents

The line, however, Should NOT touch the walls of the cave



This tic represents the direction you are looking when the cross-section was drawn. The cross-sections flip if they are drawn from the opposite direction. Usually we draw them as if we are facing into the cave

This tic represents ‘up’. It is usually obvious, but as maps get copied and rotated, sometimes this helps



Making Leader lines is easy:

Grab the Pen tool

Make the first tic, then draw straightthrough the passage

Click to add a point, hit shift (to draw a straight line) and draw right through the cross section

Add your last tic



Now grab your scissors tool

Place it on the leader line, outside the wall and click to cut

Do the same on the opposite side

Highlight

And delete for a perfect leader

Do the same for the Cross-section



Be Brave

Include several cross sections at a time, but take care to make sure that the relative height in the cross-sections agree with how the cave really lines up in real life. This data can be read from your compass data output



The same rules still apply about leader lines and tics, and touching the walls – regardless of how many passages you show in the cross -section



Lithology (symbols representing type of rock) can be added. Above you see the limestone surrounding the passage. Not only does this make the passage really stand out, but it shows exactly what happens – where breakdown covers rock, or water, or sand…

However, modern cave survey techniques demand that the sketcher explain whether, for example, a given wall is composed of solid limestone or whether it’s an indeterminate jumble of breakdown blocks. Simple symbols are used to show which portions of a passage outline are sediment or bedrock, and these “finish the thought” for the map viewer as well as the cartographer working from your sketches. (Jeff Bartlett – Arkansas Underground 4/2009)



I usually have the lithology as a symbol. I have various sizes based upon how large the cross sections are . These were all hand drawn



Cross sections are drawn with a solid line AND a solid fill. This allows them to block the lithology behind them



Details are then drawn on top of the cross-section on another layer

Layer control is important here



The lithography can be shaped to make it look less square with a large white brush if desired



An even more detailed technique, where applicable,is show specific stratigraphic layers. This is not particularlycommon, and requires the sketcher to haveknowledge of geology and the ability to observe thebedding planes; in some places, these are obvious to thelayman (a chert layer or nodules jutting out of a wall,for example) while in others the difference between adjacentlimestone formations can be gradational or otherwiseindistinct.However, in caves where the influence of multiple observablestrata have had a major impact on speleogenesis,the extra effort may be well worth the trouble. TheUSGS publishes a PDF list of suggested lithologic patternsfor common sedimentary rock on its website.(Jeff Bartlett – Arkansas Underground 4/2009)



Many different patterns are available at

http://ngmdb.usgs.gov/fgdc_gds/geolsymstd/fgdc-geolsym-sec37.pdf



Other Data to be added: Ceiling heightCeiling height is denoted by a number in a circle.

I usually write the number and then draw a circle around it.

For the next one, I just copy and paste, and then change the number. After a bit, you get a lot of the common numbers

For the Ceiling heights it is OK to use a line that touches the wall



However there are fonts available that will automatically provide numbers inside circles

These are from http://cavediggers.com/fonts/



Sometimes the data can be placed inside the passage.

This works well if you have enough room, but I prefer to have mine outside



In deep water, we typically use this adaptation of the symbol – which means height from water to ceiling /depth of water

Coupled with a cross-section, it can describethe passage excellently



There is no hard fast rule for how many ceiling heights you should put in a map.

You want to inform people of major changes, but not add so many that they clutter up the map



Drops are signified by squares around numbers. They should be coupled with a drop symbol.

We do this to indicate the drops, as well as to let the caver know that ropes may be required

These can be hand drawn, or are available as fonts as well

Other Data to be added: Drops



We usually designate the entrance as zero (O) datam

We can then give the height above or below the datam in areas of the cave. These are marked as the depth below /elevation above the entrance with a bar over the number

This lets us know generally what the cave is doing! In this example we can see the difference in locations of these two close but vertically separated passages

Other Data to be added: Datum (Vertical Control)



Other Data to be added: Names and Other InfoAdd as much extra data as you can. People love to know

where they are in a cave, and be able to refer to it by name. These should have leaders and the leaders should not touch the cave walls

Cross-Sections and Components Finishing the drafting Last Class we got here: The plan view of the...

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