# Locators — SeisComP Release documentation

6.9.0

# Locators

Locators receive phase picks from modules such as scautoloc, screloc or scolv for locating seismic or non-seismic sources. The solutions may include source time and location with or without uncertainties. They are used to form new origins which can be treated further.

SeisComP ships with built-in locators:

- FixedHypocenter (FH)

- Hypo71

- iLoc

- LOCSAT, the default locator in scautoloc and scolv

- NonLinLoc

- StdLoc

and a none built-in locator:

- LocExt.

While the built-in locators are well defined and documented, any other external locator routine can be added to SeisComP by configuration of the locator LocExt and custom scripts. LOCSAT and FixedHypocenter are native to SeisComP. All other locators are implemented as plugins. A plugin needs to be added to the list of loaded plugins by configuration of the global parameter `plugins` for making the corresponding locator available to SeisComP applications.

A comparison of the locators is given in the table below.

Note

The specifications given below may depend on the configuration of the respective locator. Please carefully read the documentation of the locators for optimizing their performance.

| FH | Hypo71 | iLoc | LocExt | LOCSAT | NonLinLoc | StdLoc
--- | --- | --- | --- | --- | --- | --- | ---
Applications |  |  |  |  |  |  |
phases considered by default | seismic / infrasound | seismic | seismic / infrasound / hydroacoustic | [3] | seismic / infrasound | seismic | seismic
distance ranges of application | local / regional / teleseismic | local / regional | local / regional / teleseismic | [3] | local / regional / teleseismic | local / regional / teleseismic | local / regional [4]
application with default configuration | regional / teleseismic | ❌ | regional / global | [3] | regional / teleseismic | ❌ | local / regional [1]
Algorithm |  |  |  |  |  |  |
inversion algorithm | linear | iterative | configurable | [3] | grid search | probabilistic | configurable
automatic phase renaming | ❌ | ❌ | ✅ | [3] | ❌ | ❌ | ❌
considers network code | ✅ | ❌ | ✅ | [3] | ✅ | ✅ [1] | ✅
positive station elevation | ✅ [2/4] | ✅ | ✅ | [3] | ✅ [2] | ✅ | ✅
negative station elevation | ❌ | ✅ | ✅ | [3] | ❌ | ✅ | ✅
considers pick time | ✅ | ✅ | ✅ | [3] | ✅ | ✅ | ✅
considers pick slowness | ❌ | ❌ | ✅ | [3] | ✅ | ❌ | ❌
considers pick backazimuth | ❌ | ❌ | ✅ | [3] | ✅ | ❌ | ❌
speed | fast | fast | fast - intermediate | [3] | fast | intermediate | fast - intermediate
Velocity model |  |  |  |  |  |  |
velocity model | 1D [4] | 1D | 1D | [3] | 1D | 1D / 3D | 1D / 3D [4]
independent Vp and Vs | ✅ [4] | ❌ | ✅ | [3] | ✅ | ✅ | ✅ [4]
default velocity model | iasp91 / tab | ❌ | iasp91 / ak135 | [3] | iasp91 / tab | ❌ | iasp91 / tab [1]
applies RSTT | ❌ | ❌ | ✅ | [3] | ❌ | ❌ | ❌
Hypocenter solution |  |  |  |  |  |  |
inverts for hypocenter location | ❌ | ✅ | ✅ | [3] | ✅ | ✅ | ✅
inverts for hypocenter time | ✅ | ✅ | ✅ | [3] | ✅ | ✅ | ✅
supports negative source depth | ❌ | ✅ | ❌ | [3] | ❌ | ✅ | ✅
Configuration |  |  |  |  |  |  |
native or plugin to load | ✅ | hypo71 | lociloc | locext | ✅ | locnll | stdloc
SeisComP provides locator | ✅ | ✅ | ✅ | ❌ | ✅ | ✅ | ✅
operates without external files | ✅ | ❌ | ❌ | ❌ | ✅ | ❌ | ✅
operates without custom scripts | ✅ | ✅ | ✅ | ❌ | ✅ | ✅ | ✅
Others |  |  |  |  |  |  |
remarks | intended for ground-truth tests / single-station location / any travel-time interface |  | operational at EMSC and ISC (earlier version) | any external locator can be called by a custom script | currently the fastest locator in SeisComP and the only one available to scautoloc | considers model uncertainties | uses travel-times from any travel-time interface
point of contact | SeisComP forum [24] | SeisComP forum [24] | ibondar2014 @gmail.com | SeisComP forum [24] | SeisComP forum [24] | SeisComP forum [24] | SeisComP forum [24]

- [1]: requires initial or specific configuration

- [2]: requires correction file

- [3]: depends on selected locator

- [4]: depends on selected travel-time interface