# Shape in plan

## Introduction

Hydration forms created in the Dingwall quarry are characterized by a varied morphology in the horizontal projection. And her observation, analysis in the field and during office works made it possible to classify the forms to the group. The shape (degree of elongation) determination in the plan was based on the documentation of the extent of each form on the surface (orange line in the picture below) and the use of the orthophotomap of the studied area to measure the length and width. Determination of the extent in the quarry was done using the Squid mobile application available for free, including Android system. This application allows you to scratch the extent of the hydration form directly on terrestrial or aerial photography using tablet. The identification of the extent of the form consisted in determining where the underground rock emptiness and the rock layer above it influence the relief. That task was realised by observations of the relevant morphological features and, first of all, paying attention to the rumbling during strike of hammer.

## Measurements and calculations

Wykartowanie zasięgu oraz pomiary długości i szerokości wykonano w programie ArcGIS. Określenie długości odbyło wzdłuż osi największego wydłużenia, natomiast szerokość pomierzono pod kątem prostym do długości. Następnie wyznaczono stopień wydłużenia o oparciu o wzór:

The quarry orthophotomap was created on the 5 most important fragments of the quarry using aerial photogrammetry. This map is characterized by the pixel size in the field up to several millimeters. Such accuracy gave the opportunity to identify all the details in the relief, and what is important to determine the shape in the plan also the extent, length and width.

Cartographic works of extent and length and width measurements were performed in the ArcGIS program. Length determination took place along the axis of the greatest elongation, while the width was measured at right angles to the length. Next, the degree of elongation was determined based on the formula:

s = (a-b)/a,

where:  a – length of hydration formi, b – width of hydration form.

## Classification

Depending on the value that s takes, the  hydration forms are described as follows:

for s from 0 up to 0,1 – forms round in plan,
for s above 0,1 up to 0,2 – forms slightly oval in plan,
for s above 0,2 up to 0,3 – forms oval in plan,
for s above 0,3 up to 0,4 – forms slightly elongated in plan,
for s above 0,4 up to 0,5 – forms elongated in plan,
for s above 0,5 – forms strongly elongated in plan.

Of course, there are forms deviating from the above shapes, such forms are called irregular and can take the shape of a bent croissant, or resemble a flower in their shape. Despite the irregularities of some forms, their shape has been generalized by submitting the classification to one of the six above.

## Gallery of hydration forms shapes

Below You may find 55 hydration forms documented at Dingwall in Canada presented on the orthophotomap, that was made fron 13th to 25th September 2018 year. For every hydration form were designated degree of elongation representing theirs shape in plan.

## Statistics

Below is the plot, where You may see, which shape in plan is the most often occuring among all documented hydration forms at Dingwall.