Monalanong Hill, Botswana Highpoint

Monalanong Hill, Botswana Highpoint Survey

August 7, 2025

Eric Gilbertson¹, Mooketsi Segobye², Yashon Ouma², Boipuso Nkwae²

¹Seattle University

²University of Botswana

Survey results: Monalanong Hill 1492.12m +/-0.01m, Otse Hill 1490.25m +/-0.01m (orthometric height, EGM2008 geoid, 95% confidence interval) . Monalanong Hill is 1.87m +/-0.02m taller than Otse hill and is the true country highpoint of Botswana.

Link to preprint of article: https://arxiv.org/pdf/2511.12332

I first visited Botswana in 2015 with Katie, and at that time it was unknown which peak was the highest in the country. Satellite-based digital elevation models measured Monalanong Hill and Otse hill as the two highest peaks in the country, with the same elevation within the error bounds of the measurements. All other peaks were lower, outside of the error bounds in elevation, thus the high point must be either Otse Hill or Monalanong Hill.

Otse Hill had been surveyed by standard trigonometric methods by the Botswana Department of Surveys and Mapping, but Monalanong Hill had not. Thus, it was unclear which peak was the country highpoint. A third peak in the Tsodilo Hills is sometimes reported as a highpoint contender, but it is more than 100m shorter than Otse Hill or Monalanong Hill based on Satellite DEMs, and is thus not a highpoint contender.

In 2015 we climbed both peaks, Otse and Monalanong, and my handheld GPS unit showed them within error bounds of the same elevation. In subsequent years other peakbaggers have also brought handheld GPS units up each peak, and also measured them within error bounds of the same height. (Handheld units can have vertical errors of +/-23m according to one study).

In Fall, 2024, Matt Algeo, who was living in Botswana, contacted me about trying to measure which peak was taller. He helped coordinate some discussions with professors Nkwae, Ouma, and Segobye at the University of Botswana, Civil Engineering department. They confirmed that it was not officially known which peak was the country highpoint. They said a Trimble engineer had brought survey equipment to both peaks in 2017, but measurements had too high errors to be conclusive (I later found out the 2017 measurements were in error by several meters for each peak, much more error than the difference in height between the peaks). Peakbaggers had brought handheld units to both summits, but those were also not accurate enough to be conclusive. So it was still a mystery which peak was the country highpoint of Botswana.

We eventually coordinated that I would visit in early August 2025. We secured official approval from the Botswana Department of Surveys and Mapping to survey each peak, and we would use a combination of my equipment and equipment from the University. Then we would use multipe different processing methods to process the data and determine the highpoint.

On August 6 I flew from Windhoek to Gaborone, then rented a car and drove to the University. I met with professors Ouma and Segobye and we planned out our surveys for the next day. The grand plan was Mooketsi and I would survey both peaks, taking a one hour measurement on each summit with my Trimble DA2 differential GNSS unit. We would use a heavy duty tripod from the university, and an Abney level to identify the highest point on the summit. A group of government surveyors would occupy monuments nearby at the exact same time as we took summit measurements. This would help us correct our measurements to get the most accurate possible elevations. (Unfortunately, it eventually worked out that the government surveyors were not available to occupy the monuments that day).

On August 7 Mooketsi and I drove to Mogonye village, and followed a rough dirt road to the base of the southeast face of Monalanong Hill. I had rented a high-clearance Corrola Cross, which was important to drive in on the rough road. We parked where the road makes a 90 degree turn south, at the closest point to the summit. By 9am we started hiking, following intermittent cow trails. We roughly followed my GPS track from my 2015 trip, ascending a SE rib that was a low-angle weakness between the cliff bands. The forest was generally open, with some thorn branches to occasionally push through.

Once we crested the plateau travel became faster in the more open terrain. There were occasional rock pillars on the mostly-flat plateau, and we aimed for the highest point as identified by satellite-based digital elevation models. Near this point was a tall rock pillar with a cairn on top, which we reached at 11am. We used the abney level to verify that all other rock pillars in the vicinity were shorter. We were on the highest point of Monalanong Hill.

We tried to mount the big tripod on the summit, but the summit was too small. My mini flexible-leg tripod fit, though, so I set up the DA2 and started logging data. By 12:30pm we had logged an hour of data, so packed up and headed down. We made good time following the same up route, and reached the car by 2pm.

There was still plenty of time in the day, so we drove down to Otse village. I turned on the dirt road just north of the peak, and followed it along the southern fence of the police academy. In 2015 I had followed this route, but had a low-clearance car and had to walk part way. This time I had a high clearance vehicle, but soon the road deteriorated and had lot of thorn trees overhanging into it. They were scratching the car up, but I kept pushing forward. It was important to drive as far as possible to give us the shortest hike possible in the dwindling daylight. Eventually the road got completely washed out, though, and I had to back up.

We drove back to the main road and then to the main entrance at the north end of the police academy. Just before the entrance gate, we turned right and followed a dirt road along the perimeter. It eventually turned south, and got rough and sandy. I kept making progress until I was 1km from the end of the road. There it was too rutted out to proceed. In 2015 that section of road was in good shape, likely because the magnesium mine at the end was operational. I think it has now been abandoned.

By 4pm we parked the car and started walking, and soon reached the old abandoned mine. Mooketsi decided to wait there and I continued up. I basically went straight up, just climbers right of the mine. The forest was mostly open, with occasional dense thorny sections. By 4:45pm I crested the summit, marked by a large concrete monument. The top of the monument says Otse 21.

I took out my abney level and verified a boulder about 3m from the summit was the highest point. It was covered in a bush that must have grown over since 2015. I cleared off some branches and mounted the DA2 on the top. I then hung out taking pictures for an hour, until just at sunset I was able to stop the recording. About that time I heard some howling and saw some rustling tree branches, and it appeared a few baboons were making their way to the summit.

I threw rocks in their direction and yelled, and they yelled back. Inconveniently, I needed to descend then, and move past them. I packed up, then found a good stick to hold and threw a bunch of rocks over towards them. They eventually moved away, but I kept the stick just in case.

I made quick progress down to the road, and we made it back to the car just before needing headlamps. We then drove back to the University to drop off equipment. The next morning I took the car to a car wash and the guys were able to smooth over all the scratches, so the car looked brand new again. I then flew out back to the US that afternoon.

I processed the results with TrimbleRTX, then I converted the files to RINEX and Mooketsi processed them using local base stations using PRIDE-PPPAR software. Results were consistent, and the PRIDE-PPPAR results had lower errors, so those will be reported as the final results.

Monalanong Hill is 1492.12m +/-0.01m, Otse Hill 1490.25m +/-0.01m (orthometric height, EGM2008 geoid, 95% confidence interval) . Monalanong Hill is 1.87m +/-0.02m taller than Otse hill and is the true country highpoint of Botswana.

Link to technical document about the work: Determination of the National Highpoint of Botswana

 

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