Explanation of Gravity Hill of Mainpat by using digital Elevation Modeling

Dushyant Kumar Rajwade

Department of School Education Surajpur Chhattisgarh, SAGES Nawapara Surajpur

dkr786786@gmail.com

Abstract: Gravity hills are present all over the world. They are known as an antigravity hill, where laws of gravity fail, whereas it is just an optical illusion. This article is a systematic study of one of such places located at Mainpat of district Surguja Ambikapur Chhattisgarh. It is a recently discovered place and is one of the most visited tourist spots. Due to a lack of scientific approach, people assume it as a magnetic effect that attracts cars uphill. There is a stream of water moving uphill due to which it is also known as Ultapani, which means water with the reverse flow. By creating a Digital Elevation Model of Ultapani 3D map, elevation profile, a contour map is prepared, which gives the actual slope of the site. It is clear from data analysis and physical verification; there is no mysterious force or magnetic force that attracts water upstream. This is first attempt to explain that water is moving downhill due to gravity.

Keywords: Gravity Hill, Digital Elevation Model, Mainpat, Ultapani, Chattisgarh, Optical illusion

Introduction

Mainpat, also is known as Shimla of Chhattisgarh, is a famous tourist attraction in Ambikapur, 5o km away from district headquarter at latitude 22°52'41.11"N. At Birsapani Ultapani, there is a small stream of water that appears to be going uphill against the slope. Tourist misunderstood it as there is some magnetic force or mysterious force which attracts water uphill. By using the digital mapping technique, we can determine the actual slope of any place by using Google Earth pro, an application software available online for free by Google Inc. It can be easily demonstrated by a simple inclinometer that there is no anomaly; due to natural landscape, there is a shift in the horizon. This false horizon makes an optical illusion, where one of the keen senses of sight misjudge the perception, and we get what is known as a spooky hill.Bresson, Garloschelli, and Barrocona (2003)   studied and found many natural antigravity sites and recreated similar conditions with no interventions whatsoever of the magnetic, ant gravitational, or otherwise mysterious force. They concluded that the optical illusion is due to inclination is misjudge relative to an estimated eye level.

Descriptions of location

Birsapani Ulatapani in Mainpat is at a height of 1,085m above the sea level. Since it is the most visited tourist place in Ambikapur Chhattisgarh it is easily assessable by any medium of transport, by road it is just 50 km away from district headquarter. Tourists generally crowd the site due to its natural landscapes and beauty. Trees and mountains surround Birsapani; there is a small dam from where the small stream originates and goes uphill to approximately 196 meters. The overall length of the stream is 196m. There is the road just parallel to it of 222 meters. Tourist put their car in neutral, and the car starts speeding uphill from point A to point B, as shown in figure.

Observation at the site

1. A small piece of paper moves upstream when placed on the water stream.
2. The neutral car appears to moves uphill.
3. The inclinometer shows variation from the visual observation (point B shows lower inclination than A).
4. Theodolite and auto-level also show an opposite inclination.
5. The magnetic compass shows no magnetic anomalies.

Methodology

We use the following methods for data acquisition and map plotting.

1. Preparation of DEM
2. Physical verification on-site by theodolite, auto level and, inclinometer

Preparation of digital elevation model (DEM)

A digital elevation model is three-dimensional representation of terrain surface created by using elevation data (Balasubranian et al. 2017). There are three main types of structure used, which are as follows.

1. Regular square grid
2. Triangular irregular network (TIN)
3. Contour

Method to prepare DEM

We can plot a contour map by using Google Earth Pro 2018 and an application software Qgis. The contour map has tags for elevation points. These elevation points give essential information to create Elevation data. The data collected is used to incorporate elevation at every grid point.

DEM can also be created by using data collected by an actual field survey, but due to convenience, we prefer remote sensing. Gridded digital elevation model consists of regularly placed uniform grids with elevation information of each grid point. A grid size of the data defines the accuracy of GDEM. The TIN structure can prepare a better DEM. It uses irregular sampling points connected by non-overlapping triangles. A most convenient method to obtain DEM is by using a contour maps-based structure. It uses mean sea level as a datum, and contour lines join the same location point. The software can generate polygons by using these contour lines, which are elevation information. Application software like Asrcgis or surfer v17 and Qgis can prepare a 3D map by using elevation points. Although these data and 3d models are reliable, there is a relative comparison for reliability of geospatial data obtained by Google Earth pro-2018 by Mohammad et al. (2013). Rusli et al. (2014) also have a similar comparison by using statistical analysis.

Reliability of geospatial data obtained by google earth

Rusli et al. (2014) compared watershed boundary by Google earth, SRTM (Shuttle Radar topography mission), ASTER 30, and ASTER 40 (Advance spaceborne Thermal Emission and Reflection Radiometer) and concluded that quality of Google Earth's elevation data is similar to SRTM90 data; however, its quality becomes better and similar to ASTER data at higher altitude. DEM from Google Earth is an easy and useful tool for geomorphologic and geospatial study and it is closely related to DEM obtained from SRTM and ASTER.

Jamil et al. (2018) used the same methodology for the survey of Al Madinah, Saudi Arabia, for data selection he uses Google earth pro 2018 and 3d model by using Surfur v13 developed by Golden Software LLC Colorado, USA. Kringing method was used, which is not a perfect interpolator. The longitudinal section profile proves the exact cause of the gravity hill. By local perception, the slope of the gravity hill seems wrong. From DEM and SRM of Al Madinah, Saudi Arabia, it is clear that the mountains around the valley obstruct the natural line of reference of the global horizon, and downhill seems uphill.

Data collection

DEM of the area under consideration is 43147sqm. The length of the road and stream of water is 222m and 196m, respectively. Google Earth Pro 2018 obtains elevation data points and converts these elevation points into keyhole markup language files (*kml), again this data file is converted into comma-separated value (*csv) file finally into a 3d

Study of Ultapani by google earth pro 2018

Figure 2

Figure 2, represents the contour map of the site, the area under observation is 43147 square meters, it is clear from the contour line there is a remarkable difference in height at point A and B. contour line shows elevation at the point A and point B is respectively 1005m and 989m. A is at a higher level than that of B from sea level. From figure 2, we get similar observations for points C and D, which are on the stream of water, it also shows C is at a higher elevation than that of D. Total length of road understudy is 222m. Moreover, the stream of water is 196m. The average slope for road and stream of water is 6.8 to -8.6% and 7.7 to -14.6%, respectively.

In this research paper, we will explore the process of generating contour lines from a Digital Elevation Model using the free and open-source Geographic Information System software, QGIS. First, we need to download the QGIS software from the QGIS.org website and install the latest version (Nkeki & Asikhia, 2014). Next, we need to obtain a Digital Elevation Model GeoTIFF file, which can be downloaded from various online sources. Once we have the DEM file, we can open it in QGIS by going to the "Layer" menu, selecting "Add Raster Layer," and then navigating to the DEM file. The DEM file will appear in the main window, where the lighter areas represent higher elevations and the darker areas represent lower elevations. To add contour lines to the DEM, we need to go to the "Raster" menu, select "Extraction," and then choose "Contour." This will allow us to select the input DEM file and specify the output file for the contour lines. We can edit the interval between the contour lines to the desired value, such as 0.5 meters, and then hit "OK" to generate the contour lines. The contour lines will be stored as a shape file, which can be displayed in the "Layers" panel. To customize the appearance of the contour lines, we can right-click on the layer in the "Layers" panel, select "Properties," and then choose the color and line width for the contour lines. (Wang & Zhao, 2021) (Barman & Sagar, 2023) (Aumann et al., 1991) (Sulaiman et al., 2012)

The longitudinal elevation profile of a road

The longitudinal elevation profile of a road, as shown in Figure 3, provides valuable insights into the terrain and slope characteristics that can significantly impact the motion of a car traveling along the route. According to the information provided, point A is located at an elevation of 1005 meters, while point B is situated at 989 meters. The difference in elevation between these two points is a crucial factor in determining the slope, which is essential for understanding the dynamics of the car's motion from A to B.

As highlighted, there is variation in the slope at different sections of the road, and the minimum elevation is at point X. Analyzing the slope characteristics along the road segment is essential for understanding the safety and efficiency of the car's movement. Slope is a critical landscape metric that can be measured as the rise over the run. Accurate slope estimation is crucial for various applications, including estimating soil loss and chemical movement, as well as for slope stability analysis and highway design. (Srinivasan & Engel, 1991) (Arifani & Prakoso, 2019) (Peng et al., 2008)

                          Figure 3                                                                                Figure 4

Figure 5

Longitudinal profile of water stream

From the longitudinal elevation profile of the water stream in figure 6, it is clear, point C is at height 1001m, and point D is at the height 989m. This account for the slope which makes the stream of water flow uphill from C to D. There is also variation in slope at different section; minimum elevation point is at Y.

Estimated slope of road 6.8 to -8.6%

Estimated slope of the water stream is 7.7 to -14.6%

Figure 6                                                           Figure 7

Figure 8

Physical verification of Ultapani

The inclinometer is when placed at 30 different points, it again shows inclination is from A to B and C to D. by setting a datum for theodolite and auto level similar result is obtained. All survey instruments used are used by professional engineers to minimize errors. The magnetic compass shows no anomalies in the magnetic field.

Concept of optical illusion

Ldesawa (1997), studied visual mechanism with optical illusion; according to him, visual observations that our sense perceives and predicts different from actual reality; this is an optical illusion. It may also affect our mortar senses and sense of grasping, Optical illusion studies by Franz (1999) showed that our brain process information coming from eyes and compare it from our memories of perception then predicts the appearance, due to which we observe these illusions in nature. The magician also uses these blind spots of the visual sense to create tricks or so-called magic. So, what we see may not always be right; sight is not a real sense.

There are many natural optical illusions around us; the formation of mirage and looming are some of these illusions. In case of a gravity hill, it is clear from our observation that there is no mysterious force or magnetic force which attracts object uphill. The site under observation consists of hills all around, which restrict the sense of horizon. In the presence of this false horizon observer in a local frame, misjudge the slope in the global frame and predict the opposite slope. DEM also confirms that the slope of Ultapani is the same for the road and stream of water. The elevation profile is an easy way to show the relative slope of the road and stream. Data collection, 3D modeling, contour mapping may not be 100% correct, but surveying instruments used at site verify that the local observer misjudges slope.

Representation of gravity hill

Figure 9, represents a gravity hill shows that the slope of local frame appears higher at B than A, but in global frame is slope is from A to B. hence a car moves from A to B. Size of landscape is large in comparison with the observer, only small part of landscape is visible, mountains and position trees also accounts for optical illusion. It is easy to create a gravity hill illusion by using the model in figure 9.

Figure 9

Conclusion

This research has demonstrated that the perceived "uphill" flow of water at Ultapani, Mainpat, is a compelling example of an optical illusion, a gravity hill phenomenon. Through the application of Digital Elevation Modeling, we have analyzed the terrain and revealed the subtle downward slope that underlies the illusion. Our findings align with similar studies conducted on gravity hills worldwide, confirming that the perceived uphill movement is a product of the surrounding landscape's influence on human perception, rather than any anomalous magnetic or gravitational forces. The slight incline of the valley, masked by the surrounding topography, creates a deceptive visual experience, leading observers to misinterpret the water's true downhill flow. This study underscores the importance of rigorous scientific investigation in debunking popular misconceptions and highlights the power of DEM as a tool for understanding and explaining such natural phenomena. Further research could explore the specific perceptual factors that contribute to the illusion at Ultapani and investigate the prevalence of similar gravity hills in the region.

Acknowledgment                                            

For this article, we had to take the help and guideline of some respected persons who deserve our most enormous gratitude. We should like to show our gratitude to Er. Harshit Rai and Er Sheetal Jaiswal for their support and guidance.

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