W celu założenia kołowej powierzchni próbnej na płaskim terenie o powierzchni 1 ara należy wybrać promień (r) o długości <br><br> <table><thead><tr><th rowspan="1" scope="col">Kąt nachylenia</th><th colspan="6" scope="col">Wielkość powierzchni próbnej (ha)</th></tr><tr><th scope="col"></th><th scope="col">0,005</th><th scope="col">0,01</th><th scope="col">0,02</th><th scope="col">0,03</th><th scope="col">0,04</th><th scope="col">0,05</th></tr><tr><th scope="col"></th><th colspan="6" scope="col">Skorygowany promień koła (\(r_1\)) w metrach</th></tr></thead><tbody><tr><th scope="row">0</th><td>3,99</td><td>5,64</td><td>7,98</td><td>9,77</td><td>11,28</td><td>12,62</td></tr><tr><th scope="row">5</th><td>4,00</td><td>5,65</td><td>8,00</td><td>9,79</td><td>11,30</td><td>12,64</td></tr><tr><th scope="row">10</th><td>4,02</td><td>5,68</td><td>8,04</td><td>9,85</td><td>11,37</td><td>12,72</td></tr><tr><th scope="row">15</th><td>4,06</td><td>5,74</td><td>8,12</td><td>9,94</td><td>11,48</td><td>12,84</td></tr><tr><th scope="row">20</th><td>4,12</td><td>5,82</td><td>8,23</td><td>10,08</td><td>11,64</td><td>13,02</td></tr><tr><th scope="row">25</th><td>4,19</td><td>5,92</td><td>8,38</td><td>10,26</td><td>11,85</td><td>13,26</td></tr><tr><th scope="row">30</th><td>4,29</td><td>6,06</td><td>8,58</td><td>10,50</td><td>12,12</td><td>13,56</td></tr><tr><th scope="row">35</th><td>4,41</td><td>6,23</td><td>8,82</td><td>10,79</td><td>12,46</td><td>13,94</td></tr></tbody></table>

• A5,64 m
• B3,99 m
• C9,77 m
• D7,98 m