Peru – the GPR archaeological surveys

Location: the area neighbouring the Pachacamac complex in Lima (Peru).
Survey objectives: stating the designation of the area between the complex and the wall in the distance of a few hundred metres.
 

Mr. Makowski at GPR survey area in Pachacamac

The working area in Pachacamac
Prof. Makowski present the place of our future struggles.

Preliminary surveys
 

Before the works began, surveys with three different antennas (a 150 MHz dipolar, a 500 MHz shielded and a 750 MHz horn) had been carried out in order to choose an optimal signal.


Because of the limited time of emission and relatively large area, it was decided to carry out preliminary surveys. A 50 MHz shielded antenna was selected for this on the basis of tests.


The profiles of preliminary surveys were run alongside 10 main lines. The survey permitted to separate places of higher intensity of anomalies, which was tantamount to increasing the accuracy of the GPR surveys.


The areas A1 and A2 were determined to establish the existence of a road other than the one visible in the picture and were not included in the preliminary survey.



The results of preliminary works show that it is not necessary to profile to the depth lower than 2 m maximum, therefore the detailed surveys were carried out with a 750 MHz antenna. The existence of a large number of small- and medium-sized stones, which would be an obstacle for a standard antenna, also contributed to such a choice of antenna. Owing to the horn type antenna of the frequency of 750 MHz (operating at a distance from the ground) we gained vertical resolution and time, which would otherwise have to spend for stone removal.


The detailed surveys carried out on separated - in the previous stage - areas are characterised by a large number of anomalies.


The existence of former foundations was shown in all areas being surveyed.

 

 

The results of preliminary works show that it is not necessary to profile to the depth lower than 2 m maximum, therefore the detailed surveys were carried out with a 750 MHz antenna. The existence of a large number of small- and medium-sized stones, which would be an obstacle for a standard antenna, also contributed to such a choice of antenna. Owing to the horn type antenna of the frequency of 750 MHz (operating at a distance from the ground) we gained vertical resolution and time, which would otherwise have to spend for stone removal.


The detailed surveys carried out on separated - in the previous stage - areas are characterised by a large number of anomalies.


The existence of former foundations was shown in all areas being surveyed.


The area A results are shown beside. The area was added in the last stage of the detailed surveying in order to verify whether a road other than the current one had run there. The results show a contemporary cobbled road (also visible in the aerial picture) and numerous groups of anomalies forming a line.

 

 

The area B consists of three surveys: B1, B2 and B3. The area B3 was distinguished by remaining foundations visible from the surface.


The GPR surveys showed numerous and clearly visible remains of foundations in the remaining areas B1 and B2.


The area B3 also contains remains of foundations.