3. Tape. Lines of taping must be well planned, with triangle ties to secure the angles. Pulling up straight is difficult in a wind, especially on broken ground, and one per cent. error is quite possible then. When working alone peg the tape down by the ring, or round a stone.
4. Tapes and cross lines. Stretch two strings crossing squarely on the ground: fix the square by laying a squared drawing block below and looking at strings over it. Two helpers each hold a tape, zero on a string, and the two tapes are held together by the observer and read off, giving the distance to each string; this is to be plotted at once on squared paper, and the plan is completed in detail as it progresses, without any note– book or later plotting. The helpers must be capable of holding the tape square to the string. Good for sites up to two hundred or three hundred feet.
5. Plane table. Excellent for some ground, where objects are visible from a distance: otherwise it requires a marker put up at every point to be fixed. Cumbrous to carry, much slower than 4.
6. Box sextant, used as giving angular accuracy to any of the foregoing; most useful with taping, and in following.
7. Sextant and three points. The most rapid accurate method is to adopt three points visible all over the ground (as trees or chimneys) or set up three markers. Find shape and size of this triangle. Then at any point take two angles visible between the points, and this fixes position of observer. A large site may have forty points fixed in two hours thus to about 1 in 1000. For detail and plotting see Petrie, Methods and Aims in Archaeology
8. Theodolite. For the most accurate work a theodolite is used, giving points to about 1 in 5000. It is almost essential for any astronomical meridian or latitude.
None of these methods necessitate any helper, except 4 which needs two helpers. The observation is from the point to be fixed in 1, 2, 3, 4, and 7; but it is to the point, needing signals or visible features on the points, in 5, 6, and 8, and for those methods a large stock of rods must be taken, and the whole ground gone over, before the work of observation; such methods take far more time than the others. The able surveyor will know by instinct how to use all the inferior methods as supplements to the higher, whenever time demands and accuracy allows.
When first searching a site, note the direction of any wall to the horizon point, and so see if other walls are parallel.
In all cases a plumb line is wanted for alining foundations and scattered blocks. Always carry six feet of thin string, and pick up the nearest suitable stone for a weight, up to three or four pounds in a wind.