source: git/doc/3dformat.htm @ 8c4cefb

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1<!DOCTYPE HTML PUBLIC "-//W4C//DTD HTML 4.0 Transitional//EN">
2<HTML><HEAD>
3<TITLE>Survex 3d Format Specification</TITLE>
4<STYLE type="text/css"><!--
5BODY, TD, TH, CENTER, UL, OL {font-family: sans-serif;}
6TD, TH {font-size: 11pt; vertical-align: top;}
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8.code {text-align: center; white-space: nowrap;}
9.type {text-align: center; white-space: nowrap;}
10.data {text-align: left; white-space: nowrap;}
11.desc {text-align: left; white-space: wrap;}
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13TH.data, TH.desc {text-align: center;}
14.reserved {background-color: #ddd;}
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16</STYLE>
17</HEAD><BODY BGCOLOR=white TEXT=black>
18<H1>Survex 3d Format Specification</H1>
19
20<P>If you're writing in C or C++ it's <b>strongly</b> recommended
21that you use the img routine provided with Survex to read and write
223d files.  Doing so means that you can take advantage of any revisions
23to the 3d format by simply rebuilding your software with the updated
24img routines, rather than having to update your own code.  It also
25allows you to read a sub-set of the data in the file, restricted by
26Survey prefix.</P>
27
28<P>This document only describes the most recent revision of the 3d format
29(version 8) which is produced by versions from 1.2.7.  A <a
30href="3dformat-old.htm">separate document</a> describes older versions.
31</P>
32
33<P>If you try to use this specification and find details which aren't
34spelled out clearly enough (or at all!) or any errors, please let us know.
35At least two people have successfully written code to read 3d files
36using this document, but that doesn't mean it can't be improved.
37</P>
38
39<H2>File Header</H2>
40
41<P>This consists of:</P>
42
43<ul>
44<li> File ID: the string "Survex 3D Image File" followed by a linefeed
45(decimal 10, hex 0a). [Note: v0.01 files can have a carriage return
46before this and other linefeeds - this is a file format error in any
47other format version].
48<li> File format version: "v8" followed by a linefeed.
49Any future versions will be "v9", "v10", "v11", etc.
50<li> Assorted string metadata - the sublist below lists these, and they
51must appear in the order given, separated by zero bytes, with the end of
52the metadata marked by a linefeed.  More items may be added, so ignore any
53additional ones which are present.  Any trailing items with empty values
54can be omitted along with the separating zero byte before them.
55 <ul>
56  <li>Survey title: Human readable description of the data in the file.
57There's no length limit on this string.
58  <li>Coordinate system: string describing the coordinate system in use
59which can be passed to PROJ.  For a coordinate system with an EPSG code
60<code>EPSG:</code> followed by the code number can be used (we recommend
61using this if an EPSG code exists).  Similarly, an ESRI code can be specified
62with <code>ESRI:</code> followed by the code number.
63 </ul>
64<li> Timestamp: A string consisting of an '@' followed by a count of
65seconds since the start of 1970 in UTC ("Unix time_t") as a string
66(for example: "@1371300355"), followed by a linefeed.  This is intended to be
67the time the file was generated, rather than the time the survey data was
68collected.
69<li> File-wide flags: a single byte.  If bit 7 is set, this is an extended
70elevation.  All other bits are reserved - set them to 0 when writing, and
71ignore them when reading.
72</ul>
73
74<H2>Items</H2>
75
76<P>Following the header are a number of items.  The last item must be a 0x00
77byte when the current label is empty, which marks the end of the data.  The
78first byte of an item is a code identifying what the item is:</P>
79
80<table border="1" cellpadding="1" cellspacing="0" width="100%">
81<tr>
82    <th class="code">Code</th>
83    <th class="code">Type</th>
84    <th class="data">Data</th>
85    <th class="desc" colspan="2">Meaning</th>
86    <th class="version">Version</th>
87</tr>
88<tr>
89    <td class="code">0x00</td>
90    <td class="type">STYLE_NORMAL / STOP</td>
91    <td class="data">&nbsp;</td>
92    <td colspan="2">
93    Set style for following legs to tape, compass and clino.
94<p>
95    If the style is already set to STYLE_NORMAL, this code signifies the
96    end of the data in the 3d file.</td>
97    <td class="version">&ge;8</td>
98</tr>
99<tr>
100    <td class="code">0x01</td>
101    <td class="type">STYLE_DIVING</td>
102    <td class="data">&nbsp;</td>
103    <td colspan="2">
104    Set style for following legs to diving data</td>
105    <td class="version">&ge;8</td>
106</tr>
107<tr>
108    <td class="code">0x02</td>
109    <td class="type">STYLE_CARTESIAN</td>
110    <td class="data">&nbsp;</td>
111    <td colspan="2">
112    Set style for following legs to cartesian data</td>
113    <td class="version">&ge;8</td>
114</tr>
115<tr>
116    <td class="code">0x03</td>
117    <td class="type">STYLE_CYLPOLAR</td>
118    <td class="data">&nbsp;</td>
119    <td colspan="2">
120    Set style for following legs to cylindrical polar data</td>
121    <td class="version">&ge;8</td>
122</tr>
123<tr>
124    <td class="code">0x04</td>
125    <td class="type">STYLE_NOSURVEY</td>
126    <td class="data">&nbsp;</td>
127    <td colspan="2">
128    Set style for following legs to unsurveyed</td>
129    <td class="version">&ge;8</td>
130</tr>
131<tr class="reserved">
132    <td class="code">0x05 - 0x0e</td>
133    <td class="type">&nbsp;</td>
134    <td class="data">&nbsp;</td>
135    <td class="desc" colspan="3">Reserved</td>
136</tr>
137<tr>
138    <td class="code">0x0f</td>
139    <td class="type">MOVE</td>
140    <td class="data">&lt;x&gt; &lt;y&gt; &lt;z&gt;</td>
141    <td class="desc" colspan="2">
142    Set current position to the coordinates given. Coordinates
143    are 4 byte little-endian signed integers representing
144    values in centimetres (0.01 metres).</td>
145    <td class="version">&ge;8</td>
146</tr>
147<tr>
148    <td class="code">0x10</td>
149    <td class="type">DATE</td>
150    <td class="data">&nbsp;</td>
151    <td colspan="2">
152    No survey date information was specified.</td>
153    <td class="version">&ge;8</td>
154</tr>
155<tr>
156    <td class="code">0x11</td>
157    <td class="type">DATE</td>
158    <td class="data">&lt;date&gt;</td>
159    <td colspan="2">
160    Set survey date of legs: date is a 2 byte little-endian unsigned integer
161    counting days from the start of 1900.</td>
162    <td class="version">&ge;8</td>
163</tr>
164<tr>
165    <td class="code">0x12</td>
166    <td class="type">DATE</td>
167    <td class="data">&lt;date1&gt;&lt;datespan&gt;</td>
168    <td colspan="2">
169    Set survey date of legs to a range: date1 is a
170    2 byte little-endian unsigned integer counting days since the start of
171    1900, and datespan is an unsigned byte counting days from date1.</td>
172    <td class="version">&ge;8</td>
173</tr>
174<tr>
175    <td class="code">0x13</td>
176    <td class="type">DATE</td>
177    <td class="data">&lt;date1&gt;&lt;date2&gt;</td>
178    <td colspan="2">
179    Set survey date of legs to a range: date1, date2 are
180    2 byte little-endian unsigned integers counting days since the
181    start of 1900.</td>
182    <td class="version">&ge;8</td>
183</tr>
184<tr class="reserved">
185    <td class="code">0x14 - 0x1e</td>
186    <td class="type">&nbsp;</td>
187    <td class="data">&nbsp;</td>
188    <td colspan="3">Reserved</td>
189</tr>
190<tr>
191    <td class="code">0x1f</td>
192    <td class="type">ERROR</td>
193    <td class="data">&lt;legs&gt;&lt;length&gt;&lt;E&gt;&lt;H&gt;&lt;V&gt;</td>
194    <td colspan="2">
195    Error information for the current traverse.  &lt;legs&gt; is the number of
196    legs. &lt;length&gt; is the total length of the
197    traverse in cm (0.01m). E, H and V are the error and the horizontal and
198    vertical components in cm. (All values are 4 byte little-endian signed integers) </td>
199    <td class="version">&ge;8</td>
200</tr>
201<tr class="reserved">
202    <td class="code">0x20 - 0x2f</td>
203    <td class="type">&nbsp;</td>
204    <td class="data">&nbsp;</td>
205    <td colspan="3">Reserved</td>
206</tr>
207<tr>
208    <td class="code" rowspan="3">0x30 - 0x31</td>
209    <td class="type" rowspan="3">XSECT</td>
210    <td class="data" rowspan="3">&lt;label&gt; &lt;L&gt; &lt;R&gt; &lt;U&gt; &lt;D&gt;</td>
211    <td colspan="2">
212    Modify the current label buffer according to &lt;label&gt; (see below for
213    details). The updated contents of the label buffer give the full name of
214    the survey station which these dimensions were measured at.  Dimensions are
215    2 byte little-endian signed integers representing values in centimetres
216    (0.01 metres). Omitted dimensions are encoded as 0xffff.  Station flags are
217    (N &amp; 0x01):
218    </td>
219    <td class="version" rowspan="3">&ge;8</td>
220</tr>
221<tr>
222    <th>Flag (N &amp; 0x01)</th>
223    <th>Meaning</th>
224</tr>
225<tr>
226    <td>0x01</td>
227    <td>Station is last one in this passage</td>
228</tr>
229<tr>
230    <td class="code" rowspan="3">0x32 - 0x33</td>
231    <td class="type" rowspan="3">XSECT</td>
232    <td class="data" rowspan="3">&lt;label&gt; &lt;L&gt; &lt;R&gt; &lt;U&gt; &lt;D&gt;</td>
233    <td colspan="2">
234    Modify the current label buffer according to &lt;label&gt; (see below for
235    details). The updated contents of the label buffer give the full name of
236    the survey station which these dimensions were measured at.  Dimensions are
237    4 byte little-endian signed integers representing values in centimetres
238    (0.01 metres). Omitted dimensions are encoded as 0xffffffff.
239    </td>
240    <td class="version" rowspan="3">&ge;8</td>
241</tr>
242<tr>
243    <th>Flag (N &amp; 0x01)</th>
244    <th>Meaning</th>
245</tr>
246<tr>
247    <td>0x01</td>
248    <td>Station is last one in this passage</td>
249</tr>
250<tr class="reserved">
251    <td class="code">0x34 - 0x3f</td>
252    <td class="type">&nbsp;</td>
253    <td class="data">&nbsp;</td>
254    <td colspan="3">Reserved</td>
255</tr>
256<!-- Checked to here! -->
257<tr>
258    <td class="code" rowspan="8">0x40 - 0x7f</td>
259    <td class="type" rowspan="8">LINE</td>
260    <td class="data" rowspan="8">&lt;label&gt; &lt;x&gt; &lt;y&gt; &lt;z&gt;</td>
261    <td colspan="2">
262    Modify the current label buffer according to &lt;label&gt; (see below for
263    details) - if &lt;label&gt; is omitted due to flag bit 0x20 being set then
264    the current label buffer is used unmodified. The updated contents of the
265    label buffer give the survey that the leg is in. Return leg from current
266    position to coordinates given, and update current position to coordinates
267    given.
268    </td>
269    <td class="version" rowspan="5">&ge;8</td>
270</tr>
271<tr>
272    <th>Flag (N &amp; 0x3f)</th>
273    <th>Meaning</th>
274</tr>
275<tr>
276    <td>0x01</td>
277    <td>Leg is above ground</td>
278</tr>
279<tr>
280    <td>0x02</td>
281    <td>Leg duplicates data in another leg (e.g. resurvey along a passage to
282    tie into a known station)</td>
283</tr>
284<tr>
285    <td>0x04</td>
286    <td>Leg is a splay shot in a chamber (radial shots from a central point)</td>
287</tr>
288<tr class="reserved">
289    <td>0x08</td>
290    <td colspan="2">Reserved</td>
291</tr>
292<tr class="reserved">
293    <td>0x10</td>
294    <td colspan="2">Reserved</td>
295</tr>
296<tr>
297    <td>0x20</td>
298    <td>No change to label (&lt;label&gt; omitted entirely)</td>
299    <td class="version">&ge;8</td>
300</tr>
301<tr>
302    <td class="code" rowspan="10">0x80 - 0xff</td>
303    <td class="type" rowspan="10">LABEL</td>
304    <td class="data" rowspan="10">&lt;label&gt; &lt;x&gt; &lt;y&gt; &lt;z&gt;</td>
305    <td colspan="2">
306    Modify the current label buffer according to &lt;label&gt; (see below for
307    details). The updated contents of the label buffer give the survey
308    station's full name.
309    </td>
310    <td class="version" rowspan="10">&ge;8</td>
311</tr>
312<tr>
313    <td colspan="2">
314    The station flags are encoded in the bottom 7 bits of the item code:</td>
315</tr>
316<tr>
317    <th>Flag (N &amp; 0x7f)</th>
318    <th>Meaning</th>
319</tr>
320<tr>
321    <td>0x01</td>
322    <td>Station is on leg above ground</td>
323</tr>
324<tr>
325    <td>0x02</td>
326    <td>Station is on an underground leg (both may be true at an entrance)</td>
327</tr>
328<tr>
329    <td>0x04</td>
330    <td>Station is marked as an entrance (with *entrance)</td>
331</tr>
332<tr>
333    <td>0x08</td>
334    <td>Station is exported (i.e. may be used as a connection point to other
335    surveys)</td>
336</tr>
337<tr>
338    <td>0x10</td>
339    <td>Station is a fixed point (control point)</td>
340</tr>
341<tr>
342    <td>0x20</td>
343    <td>Station is anonymous</td>
344</tr>
345<tr>
346    <td>0x40</td>
347    <td>Station is on the passage wall</td>
348</tr>
349</table>
350
351<p>A &lt;label&gt; value in the table above encodes modifications to the
352current label buffer, which consist of removing the last <i>D</i> bytes
353from the buffer, and then appending the next <i>A</i> bytes from the file
354to the buffer.  <i>D</i> and <i>A</i> are encoded as follows:</p>
355
356<ul>
357<li>Read a byte - if it is non-zero then: <i>D</i> = <code>byte &gt;&gt; 4</code>, <i>A</i> = <code>byte &amp; 0x0f</code>
358<li>Otherwise (i.e. the first byte is zero):
359  <ul>
360  <li>Read a byte and:
361    <ul>
362    <li>If it is not 255 then <i>D</i> = <code>byte</code>
363    <li>Otherwise, <i>D</i> = 4 byte unsigned integer read from the file
364    </ul>
365  <li>Read a byte and:
366    <ul>
367    <li>If it is not 255 then <i>A</i> = <code>byte</code>
368    <li>Otherwise, <i>A</i> = 4 byte unsigned integer read from the file
369    </ul>
370  </ul>
371</ul>
372
373<H2>Item order</H2>
374<ul>
375<li>A continuous section of centreline is defined by a &lt;MOVE&gt; item, followed
376by one or more &lt;LINE&gt; items.</li>
377<li>&lt;LABEL&gt; items may appear anywhere in the file after the header,
378including within a &lt;MOVE&gt;&lt;LINE&gt;... sequence.</li>
379<li>Duplicate &lt;LABEL&gt; items are permitted provided they also have identical
380coordinate values. (The same coordinate values may also be shared by any
381number of different &lt;LABEL&gt; items).</li>
382<li>Stations must be defined in a &lt;LABEL&gt; item <u>before</u> being
383referenced (e.g. in &lt;XSECT&gt; items)</li>
384</ul>
385
386<P>Authors: Olly Betts and Mike McCombe, last updated: 2016-05-17</P>
387</BODY></HTML>
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