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outline of a footprint

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Fossil footprints are an important supplement to the body fossil record, given outline of a footprint abundance and nature as life traces that directly record outline of a footprint and locomotion.

Yet, the potential of analyses combining footprint and body fossil data is not yet exhausted, partly due to the slow advancement of objective and quantitative methodology in ichnology.

A central problem in applying such methods to footprint data is the inability to objectively define the margins of a footprint, especially when the footprint indistinctly grades into the surrounding sediment. Various criteria for the identification of the footprint margin have been proposed, including the point of inflexion of the footprint wall, the minimum outline, outline of a footprint, and the selection of a single contour line, amongst others Falkingham, Adding to the problem, the vast majority of ichnological publications does not specify the criteria used for defining the outline of a footprint margins.

The inability to objectively define footprint margins is highly problematic especially when quantitative methods are to be applied to analyze footprint shape, since such analyses can only generate fully objective results when based on objective input data Falkingham, The problem persists when not only linear and angular measurements but a single, two-dimensional outline abstracting the whole shape of the footprint is to be extracted. The outlines of one and the same footprint, when drawn by separate researchers, can differ considerably from each other Thulborn,which repeatedly led to calls for caution in interpreting such data e.

Furthermore, the high degree of simplification of two-dimensional outlines has been criticized, proposing that the full three-dimensional profile should be retained instead e. Nevertheless, outline drawings remain the most widely used means for distributing footprint shape data, also because most anatomical information of the footprint is contained in its outline, outline of a footprint.

Problematically, it is often not possible or desirable to excavate and archive footprints in museum collections, which is why material is often difficult to access or get degraded by weathering Bennett et al. Ichnologists, therefore, are in many cases forced to rely on subjective outline drawings presented in the literature for ichnotaxonomic attributions and comparisons with relevant material. Recent efforts to increase objectivity in footprint research rely on 3D-digitization techniques, most importantly photogrammetry, which allows for the fast and cost-effective capturing of footprint morphologies in high resolution e.

A relatively new set of methods in the field, these techniques promise to solve critical problems of collection and dissemination of footprint data, and have been recently accepted as best practice in the documentation of fossil footprints Falkingham et al. Thus, the availability of such models can be expected to further increase in the future.

Although a number of outline of a footprint for the analysis of footprint shapes exist, none can effectively solve or circumvent the problem of the definition of footprint margins. Comparative approaches using 3D geometric morphometrics e. Therefore, such methods are feasible only when foot posture, most importantly the interdigital angles, is constant, as otherwise regions of the footprint may get averaged with surrounding sediment.

Furthermore, the registration of the separate footprints still requires user-defined landmarks, which often cannot be outline of a footprint unequivocally in the absence of an objective definition of the footprint margin.

The algorithm presented herein allows for the fully objective and automatic outline of a footprint of continuous outlines based on 3D surface models of footprints, outline of a footprint. The method relies on the steepness of the footprint slope i.

The algorithm presented herein source code provided as Data S1implemented in the outline of a footprint environment R, allows for the fully objective and automatic generation of outline of a footprint outlines based on 3D surface models of footprints.

Many required functions have been already implemented in the wealth of packages available for R; these were used whenever possible, reducing the script to approximately lines of code.

The output of the script consists of vector plots. When running with support for tridactyl footprints enabled, the script will additionally return landmark coordinates, a resampled version of the objective outline with homologous points, outline of a footprint, and a vector plot including the landmarks. Import of 3D-models is achieved using the vcgImport function of the Rvcg package Schlager,which supports commonly used formats including the widely used PLY, outline of a footprint.

The supplied 3D-model should contain only a single complete footprint as well as a margin of surrounding surface. The exact extent of the surrounding margin will not alter results except when an increased margin size includes additional large-scale continuous contours that can be mistakenly recognized as forming part of the footprint margin. After import, the script rotates the point cloud of the extracted vertex point xyz-coordinates to fit the horizontal plane i.

PC1 is defined as the axis of greatest variation, with PC2 and PC3 capturing successively less variation. In most situations, PC1 and PC2 will represent the horizontal plane the plane of greatest variationand PC3 the relief i. Problematically, the point cloud can get mirror-inverted during PCA fitting as the signs of the columns of the rotation matrix are arbitrary, a problem also occurring in outline of a footprint implementations in 3D-mesh software like Meshlab tested with version v The present script calculates the Procrustes distance a measure of shape difference of a subset of points of the model before and after the PCA fit, outline of a footprint, and will mirror back when detecting a significant difference.

If the footprint is a cast convex hyporelief rather than a mold concave epireliefoutline of a footprint, it will be automatically mirrored into a mold. The scale of the input 3D model is preserved throughout the process; measurements of the generated outline can be taken from outline of a footprint the plots and coordinates returned by the script. Contour lines reduce the complex three-dimensional problem to a simpler and easier-to-handle two-dimensional one, and form the natural basis for 2D footprint outlines, outline of a footprint.

Before the objective outline can be extracted, a number of additional steps are required, including 1 the removal of contours not representative for the footprint wall and 2 the establishment of homology between the points of separate contours. Contours not representative for the footprint wall are excluded based on simple criteria.

First, all open contours are removed, eliminating structures that continue beyond the margins of the model. Second, only the longest contour of each height level is selected and kept, respectively, with all others removed. This results in a stack of continuous contours, with one contour per height level.

This approach eliminates smaller structures within the footprint that are unlikely to contain relevant information on the footprint wall Fig. An option is outline of a footprint that allows for processing multiple impression per model, which is useful in cases where the footprint is not defined by a single outline. For each additional impression, the contour selecting procedure is repeated with the contours selected for the previous stacks excluded. The resulting stack of contours may still include a number of contours that convey little or no information on the footprint wall, including roundish contours around the actual footprint.

To eliminate these contours as well, and to limit the height range under consideration, areas of all contours are computed as a measure of form difference. Starting from the middle contour of the stack, the differences in area of each contour with its next lowest or highest neighbor are compared; if the difference in area between two contours exceeds a pre-defined threshold-value, the upper or lower of this contour and all following contours are removed Fig.

Different threshold-values are defined for the lower and the upper half of the stack. An option for adjusting these values is available, allowing to influence how many lower or upper contours are to be included, possibly changing the height level of the resulting calculated outline. All footprints presented in this work were calculated using the default parameters.

Even if the starting point would correspond between all contours and if each contour would contain an equal number of equidistant points requirements not fulfilled a priorithe individual points of the separate contours would tend to deviate from each other when far from the starting point, as the shapes of the contours are not identical.

For this reason, when producing a simple mean shape, outline of a footprint, points would be averaged obliquely rather than perpendicularly to the footprint wall, leading to erroneous results. Points forming the bottleneck will be considered homologous define a line that is assumed to be perpendicular to the footprint walland the points in-between the bottlenecks will be interpolated by resampling. First, all contours are resampled to the same number of equidistant points, using points per default.

The resulting contours can be variously oriented clockwise or counter-clockwise; contours are reversed accordingly to achieve uniform orientations. Second, Euclidean distances between all possible pairs of the inner and outer contour of the stack are calculated and stored in a matrix with the dimensions n x n. The pair with the minimum distance, the first bottleneck, is then extracted, and those points of the intermediate contours are detected that are closest to a line defined by the bottleneck points.

The resulting set of homologous points is then defined as the starting point of the contours. Third, additional bottlenecks are detected to establish homology. The implemented algorithm first detects a second bottleneck on the side of the footprint opposite to the first bottleneck; two additional bottlenecks are then found on each side between the first and second bottleneck. More bottlenecks are detected within the intermediate sections if the latter outline of a footprint long enough.

In all cases, bottlenecks in proximity to existing bottlenecks are prevented, outline of a footprint, assuring a roughly equal distribution of bottlenecks along the outline Fig. Finally, the individual sections between the bottlenecks are resampled to equal numbers of equidistant points, which can now be considered homologous. The objective outline will be traced along the steepest slope of the track wall. For each point within each set of homologous points, the minimum distance between the neighboring contours outline of a footprint measured.

A set of homologous points is not always fully perpendicular to the footprint wall, especially when the section between the bottleneck points is long and contours differ much in orientation. For this reason, the algorithm does not simply compute the distances within the set of homologous points, but the distances between each of the homologous points and all nearby points within and outside of the set. The steepest slope computed this way Fig. For this reason, the algorithm does not only detect the steepest point, but takes into account the steepness at all other points.

Then, the final coordinate of the steepest slope is computed as the weighted arithmetic mean of all these points.

Points will receive equal weight only when the steepness is equal; the lower the steepness compared to the steepest slope, the less weight is given. The continuous and smooth final outline is produced by applying an approximating function to the resulting set of points. As the resulting objective outline and contour stack will be rotated arbitrarily, an algorithm attempts to rotate both outline and stack into an upright orientation.

This algorithm is based on the assumption that digit impressions are facing upwards and require a longer contour segment i, outline of a footprint. In a first step, the centroid, or center of mass, of the outline is computed. The script, outline of a footprint, as described above, can be applied to any kind of depression, as no a priori assumptions on trackmaker anatomy are introduced.

Such assumptions are required when linear and angular measurements are to be extracted or when different outlines are to be aligned for quantitative shape analysis.

Therefore, outline of a footprint, a function is included that returns outline of a footprint coordinates for tridactyl footprints, which are the most common dinosaur footprints outline of a footprint one of the most common footprint types in general. The algorithm first detects and separates the three digit impressions, assuming that the outline was correctly rotated in a more-or-less upright orientation in the previous step.

Then, the rotation angle of the outline is further refined by considering the central digit impression only, which is commonly considered to approximate the mid-axis of the footprint Leonardi et al. The two hypex points were computed by finding the lowest point between the enclosing digit impressions relative to a line connecting the landmarks at the tips of these digit impressions. The landmark on the heel region is the intersection of the axis of the central digit impression and the proximal margin of the outline.

This is expected to reveal potential systematic differences between the traditional interpretive approach and the automated approach presented herein. Human-made interpretational footprint drawings aim to capture as much outline of a footprint about outline of a footprint trackmaker anatomy as preserved, outline of a footprint. Although slope steepness is the most important criterion, the steepest slope will frequently fade out along the footprint wall to continue at a different height level, making interpolation unavoidable.

Furthermore, humans tend to make a priori assumptions about trackmaker anatomy when producing the outlines, which allows them to take into account extramorphological unrelated to the foot anatomy features and include anatomical features of interest such as digital pad impressions and claw marks. The present algorithm is successful in detecting and interpolating outlines even when the steepest parts of the slope are indistinct Fig.

It does currently not include a priori assumptions that would emphasize anatomically important details and account for extramorphological features, which keeps the algorithm simple and predictable, outline of a footprint applicable to a wide range of footprint outline of a footprint. The broad applicability is demonstrated in Fig, outline of a footprint.

In the absence of a priori assumptions, however, the outlines expectedly tend to provide less information on the presumed foot anatomy than interpretative drawings, and may be unusable in cases where track morphology is obscured by extramorphological features.

Artifacts caused by a crack running transversally through the central digit impression are shown in Fig. Additional limitations currently arise from the necessity to limit the vertical extent of the contour stack, which may exclude relevant anatomical features not captured by the selected contours. Furthermore, the described approach requires that impressions can be described by single contours, which is not the case in all cases, especially when the footprint is very shallow and indistinct.

However, a preliminary option is implemented to process footprints that are composed of more than one impression, as demonstrated with an ornithopod footprint attributed to Caririchnium kyoungsookimi from the Jindong Formation in Goseong County, South Korea Figs. This footprint is relatively shallow maximum depth is 3.

The similarity of the generated outlines with human-made interpretations is demonstrated on five fossil footprints that have been previously published in the literature Figs. All five examples are compared with published interpretative drawings that had been produced using the same 3D-models; all examples, as is the case for examples used elsewhere in this work, were processed using the same script version and parameters.

All three footprints were left by the right foot. However, the sediment bars between the digital impressions tend to be less extensive e.


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outline of a footprint


Footprint pattern. Use the printable outline for crafts, creating stencils, scrapbooking, and. Person Outline Person Template Body Template Character Outline Outline Pictures Mosaic Pictures Map Outline Body Outline Outline Drawings Students can apply what they know about who scientist are and what they study by drawing themselves as scientists. Jun 27,  · Various criteria for the identification of the footprint margin have been proposed, including the point of inflexion of the footprint wall, the minimum outline, and the selection of a single contour line, amongst others (Falkingham, ).Author: Jens N. Lallensack.