What is Ground Sample Distance (GSD) and how do I calculate it?

Ground Sample Distance (GSD) is the real-world distance represented by a single pixel in an aerial image. Formula: GSD (cm/px) = (Flight Altitude × Sensor Width × 100) / (Focal Length × Image Width in px). GeoTools Pro calculates GSD instantly with the Quick GSD bar at the top of the page.

How do I convert UTM coordinates to Geographic (Latitude/Longitude)?

In GeoTools Pro, select 'UTM → Geographic' from the Geodesy menu. Enter the Easting (E), Northing (N), and UTM Zone (e.g., 23S). The tool uses Proj4js with the selected datum (WGS84, SIRGAS2000, NAD83 and 20+ others) to convert to decimal degrees and DMS format instantly.

What is magnetic declination and why is it important for surveying?

Magnetic declination is the angle between magnetic north (compass) and true geographic north. It varies by location and time. For topographic surveys, knowing declination is essential to correct compass readings. GeoTools Pro provides real declination via NOAA World Magnetic Model (WMM) API and an analytical approximation, both with value and direction (East/West).

What is the difference between a closed traverse, bounded traverse, and open traverse?

A Closed Traverse starts and returns to the same known point, allowing full closure error verification with Bowditch compensation. A Bounded Traverse starts at one known point and ends at a different known point (useful for linear infrastructure). An Open Traverse starts at a known point and ends at an unknown point — no closure check is possible, so it is only suitable for reconnaissance surveys.

How do I export UTM coordinates to KML for Google Earth?

In GeoTools Pro, open the 'UTM → KML/KMZ' tool under the Geodesy menu. Upload a CSV or TXT file with your UTM coordinates (ID, Easting, Northing, Altitude columns), select the UTM zone, datum, layer name, geometry type (points, polygon, or linestring), and click Generate KML. The file opens directly in Google Earth, QGIS or ArcGIS.

What drone flight conditions does GeoTools Pro analyze?

GeoTools Pro Drone Flight Indices tool queries real-time meteorological data from the Open-Meteo API and analyzes: wind speed and gusts (m/s), UV index, cloud cover (%), visibility (km), precipitation (mm), K-Index for atmospheric convectivity, recommended mission speed, front/lateral overlap, mission GSD, and overall flight aptitude rating.

Is GeoTools Pro free to use?

Yes. GeoTools Pro is completely free, with no registration required. All tools — GSD calculator, UTM converter, traverse calculation, leveling, KML export and drone indices — are available immediately in English, Portuguese and Spanish.

Which geodetic datums does GeoTools Pro support?

GeoTools Pro supports 20+ datums including WGS84, SIRGAS2000, SAD69, Córrego Alegre, NAD83, NAD27, ETRS89, ED50, RGF93, OSGB36, Pulkovo 1942, Tokyo, JGD2000, GDA94, GDA2020, Cape, Hartebeesthoek94, RD New, MAGNA-SIRGAS, and GRS80. Select the active datum in the header dropdown.

GeoTools Pro – Free Topography & Geodesy Tools

GeoTools Pro – Free Online Topography, Geodesy & GSD Calculator — UTM Converter, Traverse, Leveling & Drone Flight Indices

⚡ Quick GSD

Alt. (m)

Focal (mm)

Sensor (mm)

Img (px)

— waiting —

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🛩 Photogrammetry

Ground Sample Distance

Calculates the spatial resolution (cm/px) of aerial images obtained by UAV/Drone from sensor and camera parameters.

Flight Altitude (m)

Focal Length (mm)

Sensor Width (mm)

Image Width (px)

Awaiting parameters...

🛩 Photogrammetry

Flight Indices — Drone/UAV

Check meteorological conditions and operational indices for mission planning. Enter coordinates to get real-time data.

Latitude (decimal degrees)

Longitude (decimal degrees)

Mission Altitude (m AGL)

Max Drone Speed (m/s)

Flight Condition Status

💨 Wind

—m/s

aguardando

💥 Gust

—m/s

aguardando

☀️ UV Index

—

aguardando

☁️ Clouds

—%

aguardando

👁 Visibility

—km

aguardando

🌧 Precipitation

—mm

aguardando

Índices Calculados

📊 K-Index

—

convectividade atmosférica

🔲 Overlap

—%

frontal/lateral

⚡ Mission Speed

—m/s

recomendada

🟢 Flyable

—

calcule os índices

📷 Mission GSD

—cm/px

com alt. informada

⏰ Ideal Time

8h–16h

luz solar adequada

🌍 Geodesy

UTM → Geographic Coordinates

Converts UTM plane coordinates (SIRGAS2000/GRS80) to WGS84 latitude/longitude.

Easting — E (m)

Northing — N (m)

UTM Zone

Awaiting parameters...

🌍 Geodesy

Geographic → UTM

Converts WGS84 latitude/longitude to UTM SIRGAS2000 plane coordinates.

Latitude (decimal degrees)

Longitude (decimal degrees)

UTM Zone (optional)

Awaiting parameters...

🌍 Geodesy

Geodesic Distance

Calculates the great-circle distance (Haversine) between two points on the ellipsoidal surface.

Point 1

Latitude 1 (°)

Longitude 1 (°)

Point 2

Latitude 2 (°)

Longitude 2 (°)

Awaiting coordinates...

🌍 Geodesy

Magnetic Declination

Calculates real magnetic declination via NOAA/WMM (World Magnetic Model) and analytical approximation. Both indicate value and direction (E/W).

Latitude (decimal degrees)

Longitude (decimal degrees)

Altitude (m — optional)

Year (current if empty)

Enter lat/lon and choose calculation method.

🌍 Geodesy

UTM Scale Factor

Calculates the UTM linear scale factor, projection scale factor and combined scale factor for a given position and altitude.

Latitude (°)

Longitude (°)

Orthometric Altitude (m)

UTM Zone (optional)

Awaiting parameters...

📐 Topography

Analytical Azimuth Calculation

Determines the planimetric azimuth between two points in the plane coordinate system (E, N).

X1 — Easting (Origin)

Y1 — Northing (Origin)

X2 — Easting (Target)

Y2 — Northing (Target)

Awaiting coordinates...

📐 Topography

Radiation — New Coordinate

Calculates the position of a point by radiation from azimuth and horizontal distance.

X — Station Easting

Y — Station Northing

Horizontal Distance (m)

Azimuth Format

Decimal Degrees

Awaiting parameters...

🌍 Geodesy

UTM → KML / KMZ (Google Earth)

Upload a UTM coordinate table (CSV, TXT or Excel-compatible) and convert to KML or KMZ for viewing in Google Earth or any GIS.

① Conversion Settings

Fuso UTM

Tipo de Geometry

Layer Name

Point Color

② Input Data

📄

Clique ou arraste o arquivo aqui

Formatos: .csv | .txt | .tsv

💡 Formato esperado: Colunas separadas por vírgula, ponto-e-vírgula ou tab.
Colunas detectadas automaticamente: ID/Nome, Easting(E), Northing(N), Altitude(Z)
Exemplo: P1; 558123.456; 8560234.789; 100.0
A primeira linha pode ser cabeçalho — será ignorada se não for numérica.

Configure a conversão, importe os dados e clique em Gerar.

🌍 Geodesy

Datum Transformation

Convert geographic or UTM coordinates from one geodetic datum to another. Supports 20+ datums including SIRGAS2000, WGS84, SAD69, NAD83 and all global references.

① Input Datum & Coordinate Type

Input Datum

Output Datum

Coordinate Type

② Geographic Coordinates — Input Datum

Latitude (decimal °)

Longitude (decimal °)

Altitude (m, optional)

Select datums, enter coordinates and click Transform.

🌍 Geodesy

Geoid Undulation (EGM2008)

Convert ellipsoidal height (h) from GPS/GNSS to orthometric height (H) above mean sea level using the EGM2008 global geoid model. H = h − N.

① Location & Ellipsoidal Height

Latitude (decimal °)

Longitude (decimal °)

Ellipsoidal height h (m)

Formula: H = h − N | Where: h = ellipsoidal height (GPS), N = geoid undulation (EGM2008), H = orthometric height (topography)
⚠ Accuracy: This implementation uses EGM2008 spherical harmonic coefficients truncated to degree/order 20 — adequate for planning purposes (±0.5–3 m typical accuracy). For official surveys use the full 2190-degree model via IBGE/BG or NGS online calculator.

Enter latitude, longitude and ellipsoidal height.

🌍 Geodesy

Decimal ↔ DMS Converter

Convert geographic coordinates between decimal degrees and degrees–minutes–seconds (DMS). Works for both latitude and longitude.

① Conversion Direction

② Decimal Degrees Input

Latitude (decimal °)

Longitude (decimal °)

Enter coordinates to convert.

📐 Topography

Contour Lines

Upload a TXT/CSV file with X, Y, Z coordinates. The tool interpolates a regular grid and draws intermediate contour lines (1 m) and master contour lines (5 m).

① Point Cloud — Upload

📄

Click or drag file here

Format: .txt or .csv — columns X, Y, Z

💡 Expected format: Comma, semicolon or tab-separated columns.
Column order: ID, X (Easting), Y (Northing), Z (Elevation) or X, Y, Z
Example: P01; 558123.456; 7750234.789; 842.35
Header row is automatically detected and skipped.

② Settings

Intermediate interval (m)

Master interval (m)

Grid resolution (cells)

IDW power

Upload a point file and click Generate.

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