Vertical angles were always measured in both directions with the exception of the above-mentioned cases.
Observations for azimuth were always taken to the sun before and after noon. The direction used in the azimuth observation was also taken with the prismatic compass. The mean of the magnetic declination thus found is: East 8° 30′ plus.
Observations for latitude were taken to the sun by the method of circum-meridian altitudes, except at the town of Vilcabamba where star observations were taken.
As a matter of course, observations to the sun are not so exact as star observations, especially in low latitudes where one can expect to observe the near zenith. However, working in high altitudes for long periods, moving camp every day and often arriving at camp 2 to 4 hours after sunset, I found it essential to have undisturbed rest at night. It was beyond my capacity to spend an hour or two of the night in finding the meridian and in making the observation. Furthermore, the astronomic observations were to check the topography mainly, the latter being the most exact method with the outfit at hand.
The following table contains the comparisons between the latitude stations as located on the map and by observation:
| Map | Observation | |
| Camaná Quadrangle S | 16° 37′ 34″ | 16° 37′ 34″[66] |
| Coropuna, station 9,691S | 15° 48′ 30″ | (15° 51′ 44″) |
| Cotahuasi, " 12,588S | 15° 11′ 40″ | 15° 12′ 30″ |
| La Cumbre, " 16,852S | 14° 28′ 10″ | 14° 29′ 46″ |
| Lambrama, " 8,341S | 13° 43′ 18″ | 13° 43′ 14″ |
The other observations, with the exception of the one on the Coropuna Quadrangle, check probably as well as can be expected with the small and light outfit which we used, and under the exceptionally hard conditions of work. The observation on the Coropuna Quadrangle just south of Chuquibamba is, however, too much out. An explanation for this is that the meridian zenith distance was 1° 23′ 12″ only (in this case the exact formula was used in computing). Of course, an error or an accumulation of errors might have been made in the distances taken by the micrometer-alidade, but the first cause of error mentioned is the more probable, and this is indicated also by the fact that the location on the top of Mount Coropuna checks closely with the one determined in an entirely independent way by the railroad engineers.
For the cross-section map from Abancay to Camaná, the following statistics are desirable:
Micrometer traverse and graphic triangulation, with contours, field scale 1:90,000.
| Total time required, days | 40.5 |
| Average distance per days in miles | 7.5 |
| Average number of plane-table stations occupied per day | 1.5 |
| Average area per day in square miles | 38. |
| Located points per square mile | 0.25 |
| Approximate elevations in excess of above, per square mile | 0.25 |
| Highest station occupied, feet above sea level | 17,675. |
| Highest point located, feet above sea level | 21,703. |