**3. Results and discussions**

In the identification of the exokarstic forms, the primary input used was a mosaic of LiDAR images of terrain with a resolution of 5 horizontal m and 0.50 vertical cm, to which later a shade filter with azimuth 272° and height 30° is added (**Figure 3**). Here, dolines and uvalas with diameters between 20 and 125 m and up to 9 m of depth can be identified, as well as basic linear details of the relief. In the mosaic, one can see the geological structure of the quaternary period (old coastal mountain ranges, dunes, and marine terraces).

By applying an altimetric filter with a vertical difference of 0.50 cm, karstic formations are distinguishable. For said identification, the distribution of pixels based on their altitude values Identification of Karst Forms Using LiDAR Technology: Cozumel Island, Mexico http://dx.doi.org/10.5772/intechopen.79196 37

**Figure 3.** Elevation map with a vertical difference of 0.50 cm and terrain shading model (azimuth 227° and elevation 30°) with details about the known karst formations. Prepared by author based on LiDAR data [8].

of nearest neighbor interpolation, rated at 0.05 cm elevation, recognizing up to 16 m of altitude in the area of study [20]. For the terrain shading method, an azimuth of 272° and an elevation of 30° was used, and for the slope map, eight categories of classification were set manually,

Phase 4. Analysis of the distribution of units in the inventory and their contrast with the new models of identified forms. In each one of the models, 109 dolines and uvalas were visually identified, using the high resolution models and the contrast of the altimetric data, slope, and shading. Likewise, the information was contrasted with the 37 units reported in the previous studies. Furthermore, field trips were carried out during the months of June and July 2014 to confirm the occurrence of the dolines and uvalas, where the cartographic prospection at

In the identification of the exokarstic forms, the primary input used was a mosaic of LiDAR images of terrain with a resolution of 5 horizontal m and 0.50 vertical cm, to which later a shade filter with azimuth 272° and height 30° is added (**Figure 3**). Here, dolines and uvalas with diameters between 20 and 125 m and up to 9 m of depth can be identified, as well as basic linear details of the relief. In the mosaic, one can see the geological structure of the quaternary

By applying an altimetric filter with a vertical difference of 0.50 cm, karstic formations are distinguishable. For said identification, the distribution of pixels based on their altitude values

period (old coastal mountain ranges, dunes, and marine terraces).

where the highest category is >40° [21].

**Figure 2.** Flow diagram of the methodology.

36 Trends in Geomatics - An Earth Science Perspective

1:10,000 scale was verified.

**3. Results and discussions**

was taken into account; groups that presented values in ascending order from the center to the shores were sought out, since this characteristic indicates that there are depressions. Furthermore, a visual interpretation was done in which the identification criteria was the geometric form of said groups. In this case, the semicircular form is associated with the dolines and the irregular forms with processes of the formation of uvalas. The dimensions are congruent with that which was identified in the shading model.

Finally, with the contrast of the slope (see **Figure 4**), where the association of the semicircular forms and forms with a gradient greater than 25° – corresponding, in the majority of cases, to the borders of the uvalas or collapse cenotes – the altimetric difference was up to 8 m of depth. The units with lower gradients (<25°) and altitude contrast (up to 1 m in height) are related to dissolution dolines.

In the records of dolines and uvalas in the region of study, the existence of 37 karstic forms are reported, all of which have been reported as points (with latitude and longitude coordinates), the majority of which measure less than 10 m in diameter [1, 17]; with the interpretation of the models derived from the LiDAR data, 109 forms were able to be identified, with their diameter and depth. The cartography of all of the sites is shown in **Figure 5**.

Furthermore, the density of dolines and uvalas in square kilometers is shown in **Figure 6**. The concentration can be explained by the fact that the area of the highest relief (>10 masl), which corresponds to a marine terrace in which the karstification processes are more evident than in the periphery as well as other morphological genesis (dunes, coastal mountain ranges, lagoons, and shoals), located along the coast and the north of the island, and whose formations can be buried or subterranean (such as caverns and grottoes).

**Figure 4.** Slope map with six gradient categories. Prepared by author based on LiDAR data [8].

Although there is a new distribution model of dolines and uvalas, as well a proposal for density of karstic forms, it must be considered that in this study, the interpretation and identification of exokarstic forms follows a traditional process of relief form analysis [3, 5], based on the visual morphological differences (crests, slopes, surface, and background), known for their morphometric elements (height, slope, and depth).

this area of study, characterized by low altimetric contrast (<10 m) and by a base cartography at 1:50,000 scale. For this reason, it is not possible to identify karstic forms with dimensions less than 50 m, where the cost would be excessive, as pointed out by others authors [10, 14, 19]. New dolines and cenotes have been identified, along with the areas of greater density. However, an accurate characterization of each identified unit is needed to increase the understanding of the types of dolines (dissolution, collapse, and suffusion) and uvalas (first, second or third generation), their relation with the creation (structural or climatic) and with the type

**Figure 5.** Map of point distribution of the karst forms in Cozumel Island. Prepared by author based on data reported

Identification of Karst Forms Using LiDAR Technology: Cozumel Island, Mexico

http://dx.doi.org/10.5772/intechopen.79196

39

and intensity of the process of karstification.

[12–19] and this study.

The advantage of using LiDAR models, which are free for the public to access through the National Institute of Statistics, Geography and Informatics of Mexico, allows the processing of detailed data at a detailed horizontal scale (5 × 5 m) and at 0.05 cm of vertical height. The aforementioned was not possible until the year 2010, when LiDAR flights were carried out in Identification of Karst Forms Using LiDAR Technology: Cozumel Island, Mexico http://dx.doi.org/10.5772/intechopen.79196 39

**Figure 5.** Map of point distribution of the karst forms in Cozumel Island. Prepared by author based on data reported [12–19] and this study.

Although there is a new distribution model of dolines and uvalas, as well a proposal for density of karstic forms, it must be considered that in this study, the interpretation and identification of exokarstic forms follows a traditional process of relief form analysis [3, 5], based on the visual morphological differences (crests, slopes, surface, and background), known for

**Figure 4.** Slope map with six gradient categories. Prepared by author based on LiDAR data [8].

The advantage of using LiDAR models, which are free for the public to access through the National Institute of Statistics, Geography and Informatics of Mexico, allows the processing of detailed data at a detailed horizontal scale (5 × 5 m) and at 0.05 cm of vertical height. The aforementioned was not possible until the year 2010, when LiDAR flights were carried out in

their morphometric elements (height, slope, and depth).

38 Trends in Geomatics - An Earth Science Perspective

this area of study, characterized by low altimetric contrast (<10 m) and by a base cartography at 1:50,000 scale. For this reason, it is not possible to identify karstic forms with dimensions less than 50 m, where the cost would be excessive, as pointed out by others authors [10, 14, 19].

New dolines and cenotes have been identified, along with the areas of greater density. However, an accurate characterization of each identified unit is needed to increase the understanding of the types of dolines (dissolution, collapse, and suffusion) and uvalas (first, second or third generation), their relation with the creation (structural or climatic) and with the type and intensity of the process of karstification.

enrich the doline and uvala inventories in karst areas with little altimetry contrast. Even though in this study, new dolines and uvalas are reported, it lacks the complete verification and error estimation in the data interpretation and its concurrence with the reports in the literature.

Identification of Karst Forms Using LiDAR Technology: Cozumel Island, Mexico

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41

The density map of dolines and uvalas have a resolution of 5 × 5 m, being a detailed-scale map which serves to orientate new searches for the calibration of LiDAR data and to be able to orientate its use in the entirety of the northeastern zone of the Yucatan Peninsula, where LiDAR data are open and free to access for scientific and academic study, with the potential for application to and studies about quaternary geology, the evolution of the landscape, the evidence of the coastal dynamic, and the transformation of the landscape in the area inhabited

Thanks are due to the project Water and extreme hydrometeorological phenomenon in the Yucatan peninsula by CONACYT – REDESCLIM for their help. To the summer of scientific research for the help of student Angie Zapi and the trainee program at UQROO – University

Oscar Frausto-Martínez1,2\*, Norma Angelica Zapi-Salazar1,2 and Orlando Colin-Olivares1,2

1 Laboratory of Observation and Spatial Research, University of Quintana Roo, Cozumel,

2 Sustainable Development Division, Universidad de Quintana Roo, Quintana Roo, Mexico

[1] Mejía-Ortíz G, Yáñez ML-M, Zarza-González E. Cenotes (anchialine caves) on Cozumel Island, Quintana Roo, México. Journal of Cave and Karst Studies. 2007;**69**(2):250-255 [2] Frausto O, Ihl T, Giese S, Cervantes A, Gutierrez M. Vulnerabilidad a la inundación en las formas exocarsticas del noreste de la península de Yucatán. Memorias del VI seminario latino – Americano de geografía Física, Universidad de Coimbra, maio de 2010.

2010. Available from: http://www.uc.pt/fluc/cegot/VISLAGF/actas/tema3/oscar

[3] Nayengandhi A, Brock J. Assessment of coastal vegetation habitats using LiDAR. In: Yang X, editor. Lecture Notes in Geoinformation and Cartography – Remote Sensing and

of Applied Sciences, Jena, Germany, for the help of student Christian Koch.

\*Address all correspondence to: ofrausto@uqroo.edu.mx

by the Maya of the Yucatan.

**Acknowledgements**

**Author details**

Mexico

**References**

**Figure 6.** Density model of karstic forms by km2 in Cozumel. Prepared by author based on the identification of dolines and uvalas using the LiDAR model [8].
