DRNX — tutorial

This exercise takes you from an empty project to a complete drawing set in under 20 minutes. No data of your own is needed — the built-in demonstration terrain is enough.

The PL / EN language switch sits in the header, to the right of the version number.

Step 1 · Project

In the left panel, section 1 · Project:

• Name — the scheme name. It appears in the title block on every sheet.
• Horizontal CRS — coordinate reference system. For the demonstration data, leave EPSG:2180 (PL-1992).
• Vertical datum — selecting PL-EVRF2007-NH displays a note about a constant shift of +0.165 m with an uncertainty of ±0.035 m.

Why a shift rather than a rigorous transformation? Converting between Kronstadt'86 and EVRF2007 requires a quasi-geoid model that the browser does not load. The application applies a zonal shift and always states this on the drawing — it never implies accuracy it does not have.

Step 2 · Terrain

Click "Load demonstration terrain". A synthetic DTM loads: 420 × 320 cells at 2 m resolution, an area of 840 × 640 m with a valley falling to the south-east.

The Site plan tab shows hillshaded relief with hypsometric tinting and a linear scale bar.

Your own data

The Import file field accepts:

Limit: 16 million cells. LAS/LAZ and GeoTIFF are not supported — see *Technical assumptions*, items O‑1 and O‑2.

Step 3 · Route

The quickest path: "Demonstration route" — inserts a four-vertex polyline along the valley.

Manually: click "Draw route", then click successive points on the map. The button label changes to "Finish drawing". Undo removes the last vertex.

The route must run downhill. The final node becomes the outfall and is marked amber.

Step 4 · Loading

Rational method (default)

The application finds the critical storm itself: it evaluates ten durations from 5 to 180 minutes and picks the one producing the greatest flow. The result appears in the right panel under Design storm.

Catchments from the DTM

Set Catchments to "Delineation from DTM (D8)". The application fills terrain depressions using the Wang & Liu algorithm, derives D8 flow directions and assigns every cell to the nearest node along its flow path. On the demonstration terrain it captures roughly 28 ha out of 53.8 ha in under 300 ms.

Manual inflows

Select Method → Manual inflows. Only the value in Manual inflow at head node is then used.

Step 5 · Sizing

Click "Compute and size network". For a 15-manhole network the sizing takes a few tens of milliseconds.

What the algorithm does. It works from the outfall upstream. For each reach it starts with a gradient parallel to the ground, scans the diameter catalogue in ascending order, discards options that break any constraint, and among the feasible ones picks the cheapest — pipe cost plus excavation cost. If no diameter passes, it steepens the gradient by 0.5 ‰ and retries.

Where to check the result

• Computation table — 15 columns per reach: DN, gradient, Q, v, h, h/D, τ, Fr, invert levels, cover, trench. Fill above 75 % is shown in red.
• Compliance report — five checks per reach with OK / VIOLATION status and a reference to the rule.
• Longitudinal profile — scaled drawing with a data strip.
• Bill of quantities — linear metres by DN, excavation volume, manhole count, cost.

Step 6 · Documentation

Longitudinal profile

Set Sheet, Scale H and Scale V. The combination H 1:500 / V 1:100 gives a fivefold exaggeration, which is stated in the title block.

Click "Export vector PDF".

Scale fidelity. The drawing is authored in sheet millimetres, not pixels. The screen applies only an mm → px transform. The PDF is written from the same geometry model using the constant 1 mm = 2.834645669 pt. A 1:1 print therefore holds scale within ±0.1 %, verified by an acceptance test that measures the distance between control markers in the finished file.

Cross section

The Cross section tab. The slider selects chainage, the dropdown selects 1:25 / 1:50 / 1:100. The drawing shows terrain sampled perpendicular to the alignment, the pipe with its wall, the design water depth, the bedding, sidefill and backfill zones per EN 1610, the trench width dimension, and the earthwork area and volume.

Other exports

Advanced features

Dynamic simulation

Choose a Hyetograph (Euler II per DWA-A 118, Euler I, Chicago, triangular or block) and click "Dynamic simulation". The kinematic wave solver routes one hour of rainfall at a 5 s time step.

The Simulation tab: the time slider moves the water surface along the profile; the dashed line is the maximum depth envelope. Below it you will find the continuity error, the Courant number, and the inflow, outflow, storage and flood volumes.

The continuity error should stay below 1 %. For the demonstration network it is 0.0000 %.

Sensitivity analysis

The "Sensitivity analysis" button re-runs four cases: ψ ±20 % and rainfall ±30 %. The table reports how many reaches changed diameter and how the cost moved. It is the fastest way to confirm that a solution is not sitting on a criterion boundary.

Open channel

Section 5b. Enter bed width, side slope, gradient and Manning roughness. The output covers normal and critical depth, velocity, Froude number, tractive stress, freeboard and flow-regime classification.

3D view

The 3D view tab — terrain with the network beneath it. Drag to rotate, scroll to zoom. Vertical exaggeration is threefold.

Acceptance tests

The "Run acceptance tests" button executes 22 checks: section geometry, bisection invertibility, monotonicity, rainfall-depth preservation across hyetographs, kinematic wave continuity, open-channel invertibility, D8 area balance, scale fidelity measured on the generated PDF, topology and invert continuity.

Common situations

Disclaimer

Results support the designer. Responsibility for the design rests with the chartered engineer. Values marked [TO BE VERIFIED] derive from working assumptions and must be confirmed against the original standard text before use in documentation submitted for approval.