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API · /horizontalcurve-api

Highway Horizontal Curve API

healthy 4,627 Subscribers

Horizontal road-curve geometry as an API, computed locally and deterministically — the curve-element, stationing and design-radius numbers a highway engineer, surveyor or civil-design tool lays out a road or railway curve with. The geometry endpoint takes the radius and the intersection (deflection) angle and returns the full simple circular curve: the tangent T = R·tan(Δ/2), the curve length L = R·Δ in radians, the long chord LC = 2R·sin(Δ/2), the middle ordinate M = R(1−cos(Δ/2)) and the external distance E = R(sec(Δ/2)−1), plus the degree of curve (arc definition) = 5729.578 ÷ R, the US shorthand for sharpness. The stations endpoint lays the curve out from the PI: the PC (point of curvature) = PI − tangent and the PT (point of tangency) = PC + curve length — and it reminds you the PT is reached along the arc, not by adding the tangent again. The min-radius endpoint gives the minimum radius for a design speed (AASHTO) R = V² ÷ (15·(e + f)), where e is the superelevation and f the side-friction factor, the banking-plus-grip that holds a vehicle in the turn. Everything is computed locally and deterministically, so it is instant and private. Ideal for highway- and rail-design tools, surveying and civil-engineering utilities, and CAD/GIS road layout. Pure local computation — no key, no third-party service, instant. US units (ft, mph). 3 compute endpoints. For slope and grade use a slope API; for open-channel drainage a Manning API.

#highway #surveying #civil-engineering #road-design #curve #developer-tools
api.oanor.com/horizontalcurve-api
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Machine-readable spec so AI agents can integrate this API.

/api/horizontalcurve-api/openapi.json
/api/horizontalcurve-api/llms.txt

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Highway Horizontal Curve API — live data on the oanor API marketplace

API health

healthy
Uptime
100.00%
Server probes · 24h
Avg latency
74 ms
Server probes · 24h
Subscribers
4,627
active
Total calls
76
last 7 days
status Full status page → · 8 probes/24h

Pricing

Pick a tier — billed monthly, cancel anytime.

Free

Free

  • 5,200 calls / month
  • 2 requests / second
  • Hard cap (429 above quota, no overage)
  • 5,200 calls/month
  • 2 req/sec
  • Geometry + stations + min radius
  • No credit card
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Starter

€12.20 /month

  • 53,000 calls / month
  • 6 requests / second
  • Hard cap (429 above quota, no overage)
  • 53,000 calls/month
  • 6 req/sec
  • Degree of curve & AASHTO design
  • Email support
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Pro

€38.40 /month

  • 224,000 calls / month
  • 15 requests / second
  • Hard cap (429 above quota, no overage)
  • 224,000 calls/month
  • 15 req/sec
  • Road-design & CAD/GIS pipelines
  • Priority support
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Mega

€119.00 /month

  • 1,140,000 calls / month
  • 40 requests / second
  • Hard cap (429 above quota, no overage)
  • 1,140,000 calls/month
  • 40 req/sec
  • Firm & DOT scale
  • Dedicated SLA
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Highway Vertical Curve API — oanor API marketplace

Highway Vertical Curve API

Vertical (parabolic) road-curve geometry as an API, computed locally and deterministically — the K-value, profile-elevation and design-length numbers a highway engineer or surveyor lays a crest or sag curve out with. The geometry endpoint takes the incoming and outgoing grades and the length and returns the algebraic grade difference A = g2 − g1 (negative is a crest, positive a sag), the K value = length ÷ |A| (the headline number on every design chart), the high or low point offset −g1·L/A from the PVC, and — given the PVI station and elevation — the PVC and PVT coordinates and the turning-point station and elevation. The elevation endpoint evaluates the parabola at any station: elevation = PVC elevation + (g1/100)·x + (A/(200·L))·x², with the instantaneous grade g1 + (A/L)·x that sweeps smoothly from g1 to g2 — the smooth change of grade that makes the ride and sight line comfortable. The min-length endpoint gives the AASHTO minimum length for stopping sight distance: crest L = A·S² ÷ 2158 and sag (headlight) L = A·S² ÷ (400 + 3.5·S), with the controlling K, because a crest hides the road over the hump and a sag limits the headlight reach at night. Everything is computed locally and deterministically, so it is instant and private. Ideal for highway- and rail-design tools, surveying and civil-engineering utilities, and CAD/GIS profile work. Pure local computation — no key, no third-party service, instant. US units (ft, %, mph). 3 compute endpoints. For horizontal curves use a horizontal-curve API; for slope conversion a slope API.

api.oanor.com/verticalcurve-api

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Earthwork Volume API

Earthwork volume maths as an API, computed locally and deterministically — the cut/fill-quantity and soil-state numbers a civil engineer, estimator or grading contractor runs for a road, trench or site. The average-end-area endpoint gives the volume between two cross-sections = the mean of the two end areas × the distance between them, ÷ 27 for cubic yards — the everyday earthwork-quantity method you sum section by section down an alignment (a 100 ft²/150 ft² pair 100 ft apart is about 463 cy). The prismoidal endpoint gives the more accurate Simpson volume = length ÷ 6 × (A₁ + 4·A_mid + A₂) using the true middle-section area, preferred for payment quantities where the average-end-area over-estimate would matter. The soil-state endpoint converts between the three states earth passes through: loose = bank × (1 + swell %) (excavating loosens it, ~25 %, so you haul more cubic yards than you cut) and compacted = bank × (1 − shrinkage %) (placing and compacting shrinks it, ~10 %) — which is why a balanced cut-and-fill needs more bank cut than the compacted fill, with the load factor for truck sizing. Everything is computed locally and deterministically, so it is instant and private. Ideal for grading and site-work estimating, surveying and civil-design tools, and earthmoving calculators. Pure local computation — no key, no third-party service, instant. US units (ft², ft, cy). 3 compute endpoints. For tank/storage volumes use a tank API; for concrete mix a concrete API.

api.oanor.com/earthwork-api

 UTM Coordinate API — oanor API marketplace

UTM Coordinate API

UTM ↔ geographic coordinate conversion as an API, computed locally and deterministically on the WGS84 ellipsoid. The from-latlon endpoint projects a latitude and longitude into the Universal Transverse Mercator grid — returning the zone (1–60), the hemisphere, the latitude band letter, and the easting and northing in metres — using the Snyder/USGS Transverse Mercator series, which is accurate to a few millimetres within a zone; New York (40.7128, −74.0060) maps to zone 18N at about 583960 E, 4507351 N, and the canonical 45°N on a central meridian gives a northing of exactly 4982950.40 m. The to-latlon endpoint inverts it, recovering the latitude and longitude from a zone, hemisphere, easting and northing. Each zone is 6° of longitude wide with a 500000 m false easting on its central meridian and a 10000000 m false northing in the southern hemisphere. Latitude is valid from −80° to 84°. Everything is computed locally and deterministically, so it is instant and private. Ideal for GIS, surveying, mapping, geospatial, drone-mapping and location app developers, coordinate-conversion and grid-reference tools, and spatial software. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 2 endpoints. This is UTM on WGS84; for the polar regions use UPS and for an EPSG-code lookup use an EPSG API.

api.oanor.com/utm-api

 Soil Bearing Capacity API — oanor API marketplace

Soil Bearing Capacity API

Geotechnical foundation maths as an API, computed locally and deterministically. The factors endpoint computes the Terzaghi/Vesic bearing-capacity factors Nc, Nq and Nγ from a soil friction angle — Nq = e^(π·tanφ)·tan²(45+φ/2), Nc = (Nq−1)·cotφ and Nγ = 2(Nq+1)·tanφ. The bearing-capacity endpoint computes the ultimate, net and allowable bearing capacity of a strip, square or circular footing from the cohesion, friction angle, soil unit weight, footing width and founding depth, qu = sc·c·Nc + γ·D·Nq + sγ·γ·B·Nγ, breaking it into its cohesion, surcharge and self-weight components and dividing by a factor of safety (default 3) for the allowable value. The settlement endpoint computes the immediate elastic settlement of a footing, s = q·B·(1−ν²)·I / E, from the applied pressure, the footing width, the soil elastic modulus and Poisson's ratio. Cohesion and pressures are in kilopascals, unit weight in kN/m³ and lengths in metres. Everything is computed locally and deterministically, so it is instant and private. Ideal for civil-engineering, geotechnical, foundation-design and construction app developers, footing-sizing and feasibility tools, and engineering education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is foundation bearing capacity; for lateral earth pressure on walls use an earth-pressure API and for open-channel flow a Manning API.

api.oanor.com/soil-api

Frequently asked questions

Quick answers about pricing, quotas, and integration.

How do I get an API key for Highway Horizontal Curve API?
Sign up for free at oanor.com, generate an API key from the developer dashboard, and call Highway Horizontal Curve API with the x-oanor-key header. No credit card needed for the free tier.
What's the rate limit for Highway Horizontal Curve API?
Free tier allows 1 request per second. Paid plans scale up to 50 requests per second on the Mega tier. Hard limits return HTTP 429 above the quota — no surprise overage charges.
How much does Highway Horizontal Curve API cost?
Highway Horizontal Curve API has a free tier with 100 calls / month. Paid plans start at €12.20 / month with higher quotas and faster rate limits.
Can I cancel my subscription anytime?
Yes. Plans are billed monthly and you can cancel anytime from your billing dashboard. No long-term contracts and no cancellation fee.
Is Highway Horizontal Curve API GDPR-compliant?
All requests to Highway Horizontal Curve API go through our EU-based gateway. Your upstream API key never leaves our server and no personal data is shared with the upstream provider beyond the request you send.

Pick an endpoint from the list on the left to see its details and try it.

Code snippets

Sign up to get an API key, then call any path under your slug.

curl https://api.oanor.com/horizontalcurve-api/SOME_PATH \
  -H "x-oanor-key: oanor_test_..."
const res = await fetch("https://api.oanor.com/horizontalcurve-api/SOME_PATH", {
  headers: { "x-oanor-key": "oanor_test_..." }
});
const data = await res.json();
$ch = curl_init("https://api.oanor.com/horizontalcurve-api/SOME_PATH");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, ["x-oanor-key: oanor_test_..."]);
$response = curl_exec($ch);
import requests
r = requests.get(
    "https://api.oanor.com/horizontalcurve-api/SOME_PATH",
    headers={"x-oanor-key": "oanor_test_..."},
)
print(r.json())

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