Student guide: Data
The Data tab is where you check that the app has read your readings the way you meant. Every chart and every statistic depends on it, so look here first whenever a result surprises you.
This page also covers the Filters band, because the Filters decide what the Data tab shows.
1. Getting readings in
Choose the source at the top right of the page.
| Source | What it does | Use it when |
|---|---|---|
| Demo | Loads one of the bundled datasets, chosen under Demo dataset in the Filters. | Learning the app, or checking how a pattern should look. |
| Upload | Reads your CSV or Excel file (.csv, .txt, .tsv, .xlsx or .xls, up to 25 MB). The app then opens the Data tab. | Analysing your own field or core data. |
| Enter data | Opens a form on the Data tab where you type readings in. They are plotted as you go. | A few readings from a field notebook, or practice. |
Nothing is uploaded to a database. The file is read into memory for your session only.
The demo datasets
| Demo | What it shows |
|---|---|
| Synthetic: folded beds (girdle) | Bedding around a fold: the textbook girdle. |
| Synthetic: joint set (cluster) | One joint set: the textbook cluster. |
| Synthetic: slickensides as strike / dip / rake | Lines on fault planes, given as a plane and a rake. |
| Synthetic drillholes: bedding, joints, fault zone | Two drillholes with three structure types, a collar, a survey and lithology. Use it for the strip log and set finding. |
| Victoria, Stawell-Ararat zone: bedding (girdle) | Real bedding across folds (Geological Survey of Victoria). |
| Victoria, Lachlan Fold Belt: bedding (cluster) | Real bedding that is consistently oriented. |
| Victoria, Stawell-Ararat zone: S1 foliation | A real cleavage. |
| Victoria, Stawell-Ararat: fold axes (lines) | Real lines: fold axes as plunge and trend. |
| USGS Alaska: bedding and fractures | Real data with a strike column (US Geological Survey). |
The source of the demo you are looking at is given at the bottom of the page.
Preparing your own file
- One reading per row, with a heading row. Title rows above the headings are skipped automatically (the app looks in the first 15 rows for the headings).
- Two angle columns are needed, for example dip and dip_direction. Column names are matched loosely: case, spaces, punctuation and a unit at the end (
Dip (deg)) do not matter. - A structure-type column (bedding, joint, fault…) is strongly recommended, so you can analyse each type separately.
- Optional columns: a domain or area, a hole and depth (for strip logs and fracture frequency), and anything else you want to colour or label by.
The Input format button at the top of the page, and the templates on the About tab, show the expected layouts.
2. The Filters: telling the app what the numbers mean
The Filters band sits under the tabs and applies to every tab. On a narrow screen it folds to one summary line; tap it to open it.
Measurement type
Measurement type says what each row is. It changes how the two angle columns are read.
| Choice | The two columns are | Notes |
|---|---|---|
| Planes: dip / dip direction | dip (0-90), dip direction (0-360) | The direction the plane dips towards. The safest way to record planes. |
| Planes: strike / dip (right-hand rule) | strike (0-360), dip (0-90) | Needs the strike convention (below). |
| Lines: plunge / trend | plunge (0-90), trend (0-360) | For lineations, fold axes, intersections. |
| Oriented core: alpha / beta (planes) | alpha (0-90), beta (0-360) | Converted to dip and dip direction using the hole’s orientation. See Oriented core. |
| Lines on planes: strike / dip / rake | strike, dip, plus a rake column | Converted to the line’s plunge and trend (Aki-Richards rake). |
Why it matters: the same two numbers mean different things. 40 / 120 as dip / dip direction is a plane dipping 40° towards the ESE; as plunge / trend it is a line. Choosing the wrong type gives a chart that looks reasonable but is wrong.
When you upload a file, the app guesses the type from the column names and says what it matched in a blue note. If it found nothing, a yellow note asks you to pick the columns yourself.
The angle columns
The two column pickers are labelled for the measurement type: Dip column and Dip direction column, or Strike column and Dip column, and so on. Check them every time. A file with both dip and dip_direction and an older azimuth column can easily be matched to the wrong one.
Strike (if dip dir. is text) appears for dip / dip direction data. Some notebooks record the dip direction as a compass letter (NE) or leave it blank. If you choose a strike column here, the app works out the dip direction from the strike for those rows, and warns you on each one.
Strike convention
Strike convention chooses between the right-hand rule (the plane dips to the right when you look along the strike) and the left-hand rule (it dips to the left). It appears whenever a strike is used.
Why it matters: with the wrong convention every plane is drawn dipping the opposite way, 180° from where it should be. The help puts it plainly: “A wrong choice puts planes in the wrong place.”
Declination
Declination (°, east +) is added to every dip direction and trend. Use it when your compass was set to magnetic north and you want the results against true or grid north. East declination is positive.
Example: a joint recorded with dip direction 100° using a compass with no declination set, in an area where declination is 12° east, has a true dip direction of 112°. Enter 12.
Choosing which readings to use
| Control | What it does |
|---|---|
| Filter by structure type / category | The column that holds the structure type. |
| Include categories | The types to use, with a count of readings for each. For an upload the app starts with only the largest type, so that types are not mixed by accident. |
| Filter by domain / area (optional) | A column that divides the area: fault blocks, pits, geological domains. |
| Include domains | The domains to use. If you choose several, the app reminds you that different domains can have different structural patterns. |
| Label points with (optional) | A column whose value is shown when you point at a reading on the chart (for example a station number). |
Why analyse one type in one domain: a stereonet summarises one population. Bedding and joints together, or the two limbs of a fault-bounded block with the block boundary in between, make a pattern that belongs to neither. The help text says: “mixing them blurs the pattern.”
Count exact repeats once
This tick box appears only when some readings repeat another reading’s hole, depth and both angles exactly. That usually means the same structure was logged twice (for example under two logging priorities). Repeats are counted twice unless you tick the box, and that makes clusters look tighter than they are. Data health warns you until you decide.
Drillhole files (Upload only)
Under Drillhole files (optional) you can add a Collar file, a Survey file and a Geology / lithology file. If your structure file is an Excel workbook, sheets named collar, survey, lithology or geology are found automatically.
These give every structure its hole’s orientation at its depth (needed for alpha / beta and for the sampling-bias correction) and its position (needed for the 3D drillhole view). Between survey stations the hole’s azimuth and dip are interpolated in a straight line, and positions follow the minimum-curvature method. Hole names must be spelled the same in every file; a mismatch in spelling is the usual reason nothing matches.
3. Data health: what the app found
The DATA HEALTH bar above the table summarises the reading in one line:
DATA HEALTH Uploaded data · 1,333 rows · 1,333 selected · 1,327 usable · 6 excluded · 2 warnings
- rows: every row in the file.
- selected: the rows that pass the Filters (type, domain).
- usable: the selected rows that passed the quality checks.
- excluded: rows left out because a value is missing or impossible.
- warnings: rows kept, but with something worth checking.
Open the bar to see which file was read, the measurement type and columns used, what the app detected, and every warning about the whole dataset. Each warning says what is odd, why it matters and what to do.
The checks, and why they exist
| Check | What it catches | Why it matters |
|---|---|---|
| Missing or non-numeric angle | A blank or a word where a number should be. The reading is excluded. | The app cannot guess an orientation. |
| Dip or plunge outside 0-90 | For example 135. Excluded. | Usually a typing slip or a wrong column. |
| Direction outside 0-360 | For example 400. Excluded. | Usually a typing slip. |
| Horizontal plane / vertical line | Dip 0 or plunge 90. Kept, with a warning. | The dip direction or trend of these is arbitrary, so it means nothing. |
| Heavily rounded values | More than 60 % of values are multiples of 5. | Rounded readings produce false clusters at round numbers. |
| Identical pairs | More than 20 % of readings share the same pair of angles. | Copy-and-paste errors, or one reading entered many times. |
| Too few readings | Fewer than 3: no statistics. Fewer than 10: statistics unreliable. | Statistics from a handful of readings are not trustworthy. |
| Oriented core convention | Always shown for alpha / beta data, with the status assumed, checked or confirmed. | Alpha / beta conventions differ between sites; see Oriented core. |
4. The Readings table
The table lists every selected row with everything the app knows about it.
- original_row is the row’s place in your file, so you can find it there.
- qc_status is “ok”, “warning: …” (kept), “EXCLUDED: …” (left out by a check) or “EXCLUDED by user: …” (left out by you, with your reason).
- After it come all your file’s columns, then any columns the app added:
- for alpha / beta data, dip (from alpha/beta), dip direction (from alpha/beta) and plane source (which says whether the plane came from alpha / beta or from a measured dip);
- for strike / dip / rake data, plunge (from rake) and trend (from rake);
- set, once orientation sets have been found on the Statistics tab;
- terzaghi_weight, when the sampling-bias correction is on.
The table shows your original values. If you rotate or unfold the data on the Charts tab, the charts and statistics change but this table does not.
Each column has a filter box above it, and there is a search box for the whole table. The table shows up to 5,000 rows; the CSV download has them all.
Example: to see only the problem rows, type EXCLUDED into the filter box above qc_status.
Downloads
| Button | File | What is in it |
|---|---|---|
| Data with QC status and set (CSV) | stereonet_data_with_qc_DATE.csv | Every row with its qc_status, original row, set and weight. |
| QC report (CSV) | stereonet_qc_report_DATE.csv | Only the rows with an issue, with the issue and every column, for fixing at the source. |
| Leapfrog structural table (CSV) | leapfrog_structural_DATE.csv | Hole, depth, dip, dip azimuth, type, set and x, y, z, ready for Leapfrog. Shown only when a hole and a depth column are known. |
5. Flagged rows
At the bottom of the tab, Flagged rows lists every row the checks flagged, with its severity (error = excluded, warning = kept) and the reason. Readings you excluded yourself on the chart are not listed here; find them in the table by their qc_status.
6. Entering readings by hand
With Enter data as the source, the Data tab shows a form instead of a file.
- Type the two angles (for example dip (0-90) and dip_direction (0-360)) and a Structure type, then click Add. Values outside the range are refused with a message.
- To add many at once, open Paste several readings and paste one reading per line: two numbers and an optional structure type.
- Add example readings adds a small random set to practise on.
- The chart beside the form redraws with every reading. Automatic shows the mean or the girdle once there are 6 readings and the pattern is clear; the other choices from 3 readings.
- Download entered data (CSV) saves your readings with standard headings, so the file uploads straight back in.
Changing the measurement type clears the list, because the numbers would mean something else.
Exercise: which strike convention?
The USGS Alaska demo records each plane three ways: a strike, a dip, and a dip direction. That lets you test the strike convention.
- Choose Demo and USGS Alaska: bedding and fractures. Open the Data tab and the DATA HEALTH bar. How many rows were read, and how many are usable?
- Look at the first bedding reading: strike 236, dip 78, dip direction 326. Is 326 the strike plus 90 or the strike minus 90? Which rule does that match?
- In the Filters, set Measurement type to Planes: strike / dip (right-hand rule), Strike column to Strike of feature and Dip column to Dip of feature. Open the Charts tab. The poles should be where they were with the dip direction.
- Now set Strike convention to the left-hand rule. What happened to the poles? (They moved to the opposite side of the net: every plane now dips the other way.)
- Set it back. In your own work, how would you know which rule a notebook used? (Ask, check the field notes, or compare with a recorded dip direction as you did in step 2.)