The Hotchkiss Map Collection at the Library of Congress contains 341 sketchbooks, manuscripts, and annotated printed maps made by Major Jedediah Hotchkiss (1828-1899), a topographic engineer in the Confederate Army. The entire collection is online at the Library's American Memory Project. A good article by Clara LeGear on the history of the maps contains biographical information on Hotchkiss is available there as well: "The Hotchkiss Collection of Confederate Maps." Library of Congress Quarterly Journal of Current Acquisitions 6 (November 1948): 16-20.
The Hotchkiss map is one of the most topographically detailed maps of the battlefield. For example, compare the detail of the Hotchkiss map below with the same detail of the West Woods in the Cope/Carmen map at the end of this post. (Click on this image and all others to enlarge).I have annotated the map with blue numbers (1 through 4) and a single arrow pointing north. Each of the blue numbers indicates a "draw" or "swale" that is part of the landscape of this part of the woods. It was through these swales, especially 2, 3, and 4 that Barksdale's Brigade and the 3rd South Carolina pursued the remnants of Sedgwick's left.
(Below) Swale # 1 looking north from the fenceline of the woods. The Hagerstown Pike is just to the right.
Below swale 2 from the fence line looking north. This picture was taken from the position indicated by the blue arrow on the Hotchkiss map. The Starke mortuary cannon is in the left distance. (Below) Looking west, standing on the ridge between swales 1 and 2 with 2 in the foreground and 3 in the background (the greener swath of grass). These swales are quite deep and if you stand in them you cannot see much except the sides of the formation. Marty Pritchett, a very knowledgeable volunteer at the park, once described the field as an ocean of stone waves--the waves being the limestone ridges rolling east to west. If you walk the field, you will find yourself bobbing up and down over the waves as you move westward. Experiencing this gives you an understanding of the difficulty of maneuver and maintaining a bearing on such a landscape.
(below) Swale # 4 looking southwest past the Brockenbrough's (Maryland) Battery into the West Woods. This is the shallowest of all of the four.
Compare the Hotchkiss map and the Cope/Carmen map below. Only swale #2 above is represented on the map.
If you are tramping the field, try to carry both maps--one for the topography and one for the units.