Prof. Gachari attended the University of Oxford, Britain, for his postgraduate studies attaining an M.Sc. and finally a PhD in 1997. This was realised throughsupport of two separate scholarships both funded by the British government including the Commonwealth scholarship that fully funded the PhD studies at Oxford. For his undergraduate studies, he attended the University of Nairobi attaining a B.Sc. (Hons) in Surveying and Photogrammetry in 1981. Prof. Gachari is also a holder of an MBA (Strategic Management)(2011) attained from Kenya Methodist University.
Further, he has attended various short certificate courses including a two months course on Geodetic Control Surveying at the Geographical Survey Institute (GSI) in Tsukuba city, Japan (1988). He also attended a two months course in Advanced Geographic Information System (GIS) at the Institut Geographic Nationale (IGN) in Paris, France (1990).
Prof. Gachari has over his academic, research and scholarly career been engaged in teaching, research, as well as research and teaching based institutional development. He is widely published in his broad areas of research interest including Geomatics, GIS, Remote Sensing, Geodesy, and their broad applications. He has supervised to completion,numerous PhD, and MSc candidates as well as being continuously engaged insupervision of ongoing PhD and MSc students, and teaching of in both Postgraduate and undergraduate programmes.
Prof. Gachari started his University teaching career in 1990 after joining the Jomo Kenyatta University College of Agriculture and Technology (JKUCAT), the precursor of the current Jomo Kenyatta University of Agriculture and Technology (JKUAT) at the Department of Civil Engineering, Faculty of Engineering. While serving at the department of Civil Engineering, and apart from other contributions in the growth of the department, he was engaged in developing and teaching surveying and related courses, teaching to among others, B.Sc. Civil Engineering students, Bachelor of Architecture students, B.Sc. Agricultural Engineering students.
While still serving as a Lecturer, and Senior Lecturer in Civil Engineering Department, and as part of the B.Sc. Civil curricula review, Prof. Gachari initiated, prepared, and taught the first Geographic Information Systems (GIS) course unit into the B.Sc. Civil programand indeed in JKUAT.
Along with the GIS unit, he also proposed and guided the preparation of the first Remote Sensing Course unit facilitating its teaching. He also initiated and supervised final year B.Sc. Civil Engineering final year student projects that were GIS based. These initiatives and contributions formed the seeds towards development and growth of Geomatic Engineering and Geospatial Information Systems (GEGIS) programmes and their broad applications in JKUAT and beyond.
Further, while still serving at the Department of Civil Engineering JKUAT, Prof. Gachari spearheaded the development of the B.Sc. in Geomatic Engineering and Geospatial Information Systems (GEGIS) programme eventually serving as the first programme coordinator on receiving the pioneering cohort of students. This was later followed by development of a proposal for the establishment of a the then new dedicated Department of Geomatic Engineering and Geospatial Information Systems (GEGIS) where he was appointed the founding Chairman of the Department (CoD), a position he continued to hold for five (5) years.
During his term as CoD (GEGIS), he oversaw the rapid growth of the department in student numbers, staff attraction, recruitment, and training, facilities and infrastructure, establishment of post postgraduate programs,including spearheading the development of the initial postgraduate programmes, an M.Sc. is GIS and Remote Sensing, as well as an MSc in Environmental Information Systems. He also Supervised to completion, the pioneering PhD in GIS student in the department, and JKUAT.
Through his initiatives in sourcing and attraction of funding and resources to support training, research and institutional growth and development including laboratories, Prof. Gachari attracted funding support from Environmental Systems Research Institute (ESRI) in form of among others, GIS and Remote Sensing software (25 Licenses), and access to GIS Virtual campus enabling establishment of the first dedicated GIS and Remote Sensing lab in GEGIS department and indeed in the entire University (JKUAT). This lab was critical in supporting state of the art training and research in Geospatial technologies and their broad applications enabling quality training and research in support of both the postgraduate undergraduate programmes. The lab was later to become an important facility for training in GIS and Remote Sensing for the entire University as GIS and Remote Sensing course units that were gradually introduced in other degree programmes and all serviced from GEGIS department.
At JKUAT, Prof. Gachari also was appointed and served as substantive Associate Dean of the Faculty of Engineering, a faculty that then comprised the four departments – Civil Engineering, Electrical & Electronic Engineering, Mechanical Engineering, and Geomatic Engineering & Geospatial Information Systems (GEGIS). He also served as acting Dean of the same Faculty of Engineering for some period.
In early January 2008, and while still serving as Associate Dean, Faculty of Engineering at JKUAT, Prof. Gachari was appointed acting Principal of Kimathi University College of Technology (KUCT) a then newly established constituent college of JKUAT eventually serving in that capacity for a year. KUCT was the precursor of DedanKimathi University of Technology (DeKUT). He later served as Deputy Principal (KUCT). When the University attained a Charter and fully fledged University Status in 2012, he was eventually appointed the Deputy Vice Chancellor (Administration and Finance) a position he held for five years until 2018.
Further, while still serving the University variously in senior management and administration positions, Prof Gachari spearheaded the development and establishment of Geomatic Engineering and GIS (GEGIS), and Geospatial Information Science Remote Sensing (GIS RS) programmes at DeKUT, the department of GEGIS, and eventually leading to the establishment of the Institute of Geomatics, GIS, and Remote Sensing (IGGReS).
Further, while still serving the University in senior management and administration positions, Prof. Gachari continued supervising PhD and MSc Students. Among these students, he supervised to completion, the pioneering PhD student in the PhD in Geomatics & Geospatial Science programme in IGGReS, DeKUT.
Prof. Gachari currently serves as a Professor at the Institute of Geomatics, GIS, and Remote Sensing (IGGReS), Dedan Kimathi University of Technology.