+-- Ground level -----------------------+
| |
| * * * |
| \ / \ | |
| \ / \| |
| * * |
| | | |
| | | |
| * *--* * |
| / \ / |
| / \ / |
| * * * * |
| \ | \ / |
| \ | \ / |
| * * * |
| / / \ |
| / / \ |
| * * * * |
| \ /| | / \ |
| \ / | | / \ |
| * * * *--* * |
| / \ /| | | |
| < / \ / | | | |
| * * * * * * |
| | / | | |
| |/ | | |
| *--* * * |
| \ / \ \ |
| \ / \ \ |
| * * * * * |
| / \ / / |
| / \ / / |
| * * * |
| / / |
| / / |
| *--*--* * * |
| \ \ |\ |
| \ \| \ |
| *--*--* * * |
| /| / | |
| / | / | |
| * * * * |
| | | |
| | | |
| * M |
| \ |
| \ |
| * * * |
| / /| / \ |
| / / |/ \ |
| * * * M |
| / / |
| / / |
| *--*--* |
| |
+---------------------------------------+